- It's you.
Thought you were just the Player Character here? Nope! Frisk and the player are treated as separate entities in Undertale; the latter simply dictates the actions of the former. But remember that Undertale isn't a typical RPG, all of your choices will affect the game world... for better or for worse.
Depending on the interpretation, you either play as the Fallen Child (see their folder below) or yourself. Either way, this folder describes the role of the Anomaly.
Abstract Apotheosis: As noted in Sentient Cosmic Force, you're a being only visible in consequences that happen in the timelimes, you are the driving force in the world, it's your choices and determination that replaces Frisk's. thus if perhaps only in the "purity of action" sense of the trope or perhaps something more literal you are not just a determinator, you are DETERMINATION itself.
Above Good and Evil: Since the world of Undertale is fictional and you're not, you may find yourself trying to justify your actions this way during a genocide run. And get called out for it.
Ambiguously Evil: One of the game's primary artistic purposes is opening up questions about human morality regarding how they treat circumstances where actions have supposedly no consequences. Stereotypes aside, odds are you're not actually an evil person; you just wanted to see what would happen if you killed everybody. And hey, since you can always go back and fix everything anyway, that makes it all okay, doesn't it? It wasn't actually, literally morally reprehensible of you to do a genocide run, right? Right...?
Ambiguously Human: The common interpretation of Chara's Deal With The Devil is that they are an inhuman entity, it just dawn on me, maybe it is the player the one who is no longer human because of their actions, see Humanoid Abomination.
The Antichrist: In the Genocide run. You fit the archetype regardless if you're playing as Chara or not. A figure of unending destruction who helps bring about The End Of The World As We Know It.
As Long as There Is Evil: The fact that you exist and can restart the game at any time - erasing everyone in its memories - makes you the single most potentially evil - and unstoppable - entity in the story.
The Assimilator: You somehow make Chara personification of power gaming, stats and perfectionist tendencies in the genocide run. Probably when you call their name. When you stop playing the game they are reduced to a feeling in your head and heart.
Apocalypse Maiden: A very evil one in the genocide run, but you'll be this if you don't know what you're getting into.
Ax crazy: Up to eleven/Hoo Omnicidal Maniac/boy… In the genocide run and the darker neutral runs. One of the biggest examples in videogame history, after all, name one character who tediously hunts down an entire country and kills them one by one and if you choose to erase destroys the entire gameworld. Majin buu from Dragon Ball Z and Omega in Megaman Zero would be proud. Emphasis more on the ax than the crazy.
Badass: You can surpass and outlast the game's biggest badasses such as Sans and Undyne the undying through sheer skill and determination.
Big Bad: Your actions directly influence the course of the game and beyond, and they also decide on just how much influence the Fallen Child has on Frisk by the end. Considering how many times certain characters refer to you and not Frisk, it's safe to say your choices are acknowledged within the game, making you instrumental to the plot.
Big Bad Duumvirate: If you are playing as yourself and not the Fallen Child, they will take control by the end of the Genocide route, forming a Big Bad Duumvirate with you, though only for the Fallen to pull an Eviler Than Thou.
Dragon In Chief: See below on the entry.
Bigger Bad: In the Genocide Run. One step above the Fallen Child you're the true mastermind of the destruction happening in the game. Becoming more like a possessive, apocalyptic demon for doing what you normally do in every other videogame while being the hero: level grind and killing all the monsters.
Greater Scope Villain: With the Narrator Chara theory gaining more and more supporters, the Undertale fandom in general has come to the consensus that despite the world-destruction that Chara causes at the end of a Genocide Route, it's not really Chara's fault—it's yours for corrupting Chara to be that way in the first place. These days you'll find much more Youtube comments along the lines of "Chara's not evil, you are!" than the latter.
Big Good: You also have the choice to give everyone their happy ending... assuming you don't reset.
Blue and Orange Morality: If you play through all the routes for just the experience, Sans in the Genocide route is the only one who comes close to considering that's why someone would do that. Even more in general, [ADarkerMe/you think and behave in ways you never would in Real Life.]
Blood Knight: Many, including myself have admitted that one of the reasons to do a genocide run is to challenge Undyne and Sans.
The Corrupter: Frisk's LV (or rather, The Fallen's LV) is a measure of their Killing Intent, and the player is responsible if it's above the lowest level.
If you believe you're playing as the Fallen, you can exploit Frisk's determination to increase your own power, eventually getting them to sell their soul so you can use them to destroy timeline after timeline.
If you believe you're playing as yourself, you feed the Fallen by using Frisk to committ atrocity after atrocity. Eventually, they become corrupt enough to take control of Frisk from you completely, even in future playthroughs.
If you believe the fallen was initially not evil, then you're also corrupting them.
Cosmic Chess Game: You're a player for once instead of a pawn, you're opponent is Flowey, the only other character to use determination and also possibly Chara, though they will normally remain [SubmissiveBadass/submissive to you].
Cosmic Horror Story: You can easily turn the entire game into this if you so choose. There is no character within the game, not even Flowey or the Fallen Child, who can match the sheer cruelty you can inflict upon the world.
Dark is Evil / Dark is not Evil: There is a Epileptic Trees floating in the Internet that you are the darkness Gaster detected, whatever you're evil or good depends on how you play.
The Dark Side: You read that right, before you ask, no I'm not saying that you use the Dark Side, I'm not even saying that you play as the Dark Side. I'm saying that in this game you ARE the Dark Side, feeding Chara power and corrupting them into evil and being the Antichrist to your Satanic Archetype at the same time. (Only in the genocide run or when you kill somebody, really).
Demonic Possesion: You have complete control over Frisk, but you aren't them.
Determinator: You have to be to get one of the true endings, or even make it to the end after all the deaths you'll get, determination and the resolve to achieve what you want is one of the game's main themes and it's heavily encouraged in players to match Frisk and the fallen child.
Dragon in Chief: Depending on how you see Chara and their relationship with you, either you are this to them or they are this to you, or [BigBadDuumvirate/)you're on equal terms].
It's the Fallen Child's LOVE and stats Frisk is using.
It's YOU who actually does all the work, dodges the attacks, etc with Chara simply providing the muscle and information.
The Dreaded: It's perfectly possible to be this even though everyone will think you're Frisk, but well, basically the entire underground will fear you.
Eldritch Abomination: A being beyond comprehension, the same species as the creator of the world, utterly beyond punishment and capable of altering reality with ease. Powers include possessing children, returning lost beings back into existence, [TheAssimilator/absorbing the dead remains of somebody as part of their beings], resetting the world and, yes, even undoing what cannot be undone. No one can understand why such a being would do what it does. The only one who seems to be aware that you're a human from outside their world is Chara, who at the end of a Genocide Route states that the "human SOUL" and "determination" were yours.
Humanoid abomination: In undertale the line between Chara, Frisk and the player get extremely blurry so their "inhuman" descriptions should probably be taken to include you in the genocide run too, if that is not eldritch enough, see the Eldritch Abomination entry, so yeah, you fit straight here, especially in No Mercy, has it even occurred to you that maybe, just maybe, Chara is able to take your SOUL because you turned demonic and not them. There is fan art that exemplifies this the best on the internet, just google "player chara".
Eviler Than Thou: Invoking this is about the only way you can get a semblance of victory over the Fallen Child, baffling them with your sheer depravity.
You can also pull this on Chara simply by not selling your soul and instead deleting the game, carrying them within you forever.
See The Assimilator and Evil is not a Toy.
Evil Is Not a Toy: Thought it'd be fun to try a Genocide route and then go back and fix it again afterwards? The Fallen Child will happily and painfully remind you that life doesn't work that way.
Invoked at the end of the Pacifist Route, when Flowey reminds you of the responsibility you have of guarding the reset button.
Inverted if you choose to simply delete the game from your computer which could be interpreted in meta as you assimilating Chara as a part of yourself, truly destroying everything and move on to the next world.
Evil Makes you Monstrous: In undertale the line between Chara, Frisk and the player get extremely blurry so their "inhuman" descriptions should be taken to include you in the genocide run too.
Face–Heel Turn: Any player who gets the True Pacifist ending, resets and starts a Genocide run pulls one. You can't even use the excuse of "alternate dimensions/timelines" - the game makes it quite clear you're snatching the characters' happy ending away from them and replacing it with death, doom and despair. For a while you still have a chance to turn back, reset with virtually no damage and do a True Pacifist ending again. But if you go far enough, your actions will permanently affect the game, preventing you from ever getting the true happy ending again.note
Final Boss: Due to a Perspective Flip YOU could be considered the final boss of the genocide route. This interpretation is best explained by the fact that in most final bosses the player is the hero trying to save the world from the Big Bad boss but Sans is the hero of the battle.
The player, who's [MergerOfSouls/fused] with Chara for doing the evil route is the final enemy of Sans's game and Megalovania is their battle theme.
Fighting A Shadow: The main reason why no one can hurt YOU no matter how badly they want to. You're in Real Life, a literal higher plane of existence using Frisk as your avatar in the game world, how are they supposed to reach you? Much less do you harm?
For the Evulz: Why would anyone want to cause harm to others unless they had a reason? What was your reason? Oh, right. You did it just because you could.
Fusion Dance/Merger of Souls: With Chara.
From Nobody to Nightmare: If you choose to take the No Mercy run, you go from attacking common monsters to mutilating bosses in one hit to destroying the world with help from the fallen human.
A God Am I: Flowey will call you out on your attempts to shape destiny, especially true if you abuse it for your own amusement.
A God Is You: Type B
God Of Evil: Or the closest equivalent the game has, see A God Am I and Satanic Archetype.
Greater-Scope Paragon: In a meta sense. Since Frisk is the main character and Sans and Toriel are both technically the Big Good, that technically makes you the greater scope paragon of the entire game, since you're technically responsible for most of what Frisk does in the story...assuming that you aren't going for a genocide run, of course. That being said, on the flipside...
Greater Scope Villain:...Also in a meta sense. With the Narrator Chara theory gaining more and more supporters, the Undertale fandom in general has come to the consensus that despite the world-destruction that Chara causes at the end of a Genocide Route, it's not just Chara's fault—it's yours for making Frisk do the genocide route. These days you'll find much more YouTube comments along the lines of "Chara is evil, but so are you!" than the latter. Heck, there's even a YouTube video out there with the song "When You're Evil" regarding the player, not Chara. Given that there's no Word of God on the issue currently though, it's all open to interpretation, much like many other aspects of Undertale. This trope only applies if you're going for a No mercy/Genocide run.
Heel–Face Door-Slam: Felt bad about the Fallen Child's decision to completely destroy the world? Tough. They'll ignore you and destroy it no matter how you respond in the end. In fact, going that far leads to a permanent Heel–Face Door-Slam, as all Pacifist Runs are tainted from there on without manually altering the game's files.
The Hedonist: Sans accuses the Anomaly of never being happy, always wanting more.
Heel–Face Turn: The game allows a player on the Genocide path to step off it up until the Mettaton NEO fight. When Papyrus, for example, offers to Spare you, it's a genuine offer with no strings attached, and will set the game back to Neutral mode. Sans' offering, on the other hand, is not.
It's possible for the trope to still be played straight after the player accepts Sans' false offer of mercy, IF the player takes the skeleton's words to heart and RESETS after getting dunked on. Of course, this depends entirely on the player.
He Who Fights Monsters: Literally on the more malicious runs.
Humans are Cthulu: You're human, see the Eldritch Abomination entry.
Humanoid Abomination: In undertale the line between Chara, Frisk and the player get extremely blurry so their "inhuman" descriptions should probably be taken to include you in the genocide run too, if that is not eldritch enough, see the Eldritch Abomination entry, so yeah, you fit straight here, especially in No Mercy, has it even occurred to you that maybe, just maybe, Chara is able to take your SOUL because you turned demonic and not them.
Invincible Hero: If you're truly Determined to give as many characters as possible their happy ending, then there's nothing anyone can do to stop you; Flowey will become just a minor irritation.
Invincible Villain: There is nothing the characters can do to stop you from doing a Genocide run, aside from trying to talk you out of it or hoping you'll get bored and give up. With your Determination, every defeat is just a setback. If you want to replace their happy ending with the death of everyone, you can. If you want to kill the same character over and over again, you can. The only one you can't beat, without manually altering game files, is the Fallen Child after you've sold Frisk's soul to them.
I Want My Beloved to Be Happy: If you listen to Flowey and choose to abstain from a True Reset after getting the Golden Ending, letting the characters you've grown to know and love happily live out the rest of their lives without you. Believe it or not, quite a few fans will admit to having done this.
The Killer in Me: The true villain of the Genocide route: a crazed killer whom the lesser monsters fear and the more powerful ones die fighting heroically.
Lack of Empathy: To get the Genocide ending, you have to be seriously detached from the characters begging you to stop.
Make Wrong What Once Went Right: Should you ever reset the golden ending to do a Genocide, you are invoking this trope.
Magnificent Bastard: YMMV. If you either spoiled yourself or done it previously, you can achieve whatever ending you choose via surpassing all obstacles through foreknowledge, sheer skill and determination, manipulating everyone, even fellow Magnificent bastard and reseter Flowey like a violin to do so. The biggest Magnificent Bastard in the game.
Mistaken Identity:
If you believe you are playing as yourself and not the Fallen Child (especially given how they break the fourth wall at the end of the Genocide route), then any time Flowey addresses you as the Fallen will count as this.
A subtle example in Sans. He's the only character who confirmably knows you even exist — but while he correctly identifies you on a Genocide run as the cause of the latest resets, he doesn't seem to realize that you haven't always been the one resetting the timeline. Flowey's speech a few rooms earlier gives the impression that his reign as resetter was a Time Abyss; most likely, he was responsible for far more loops than the player ever could be. Sans never seems to realize this.
My God, What Have I Done?: The game tries very, very hard to evoke this feeling out of you the entire time you play the Genocide route, let's just put it that way.
No Kill Like Overkill: Your damage becomes ridiculously excessive in the Genocide route.
Omnicidal Maniac: In the Genocide run, which is discussed heavily throughout. To what extent are you willing to annihilate an entire world and its inhabitants just to slake your own boredom or to satisfy a completionist urge? Accordingly, the line between you and the Fallen Child is deliberately blurry and it can be hard to tell where you end and they begin.
Our Angels Are Different: The Delta Rune prophecy talks about angel, who will descend from the surface and empty the underground. Who the angel is debated with the options being Chara, Asriel, Frisk and finally the player, given that the later, us are the ones who pick the ending, it's likely that the prophecy refers to the player. Personally I don't know about you but in a page called Quotev, I've done a couple text for fun and in "What were You in a Past Life?"from NOBODYHERE I've got the following results: You were a Torn Angel
Oh, Torn Angels aren't bad, but they aren't good either. They simply can't decide. Everyday is an internal battle for them. Be bad, or be good? It's when an Angel is at a middle point between becoming Dark and staying Light. At this point, there's still a chance to save them. Humans who were once Torn Angels are often indecisive and don't seem to really know what's happening. They are often incredibly moody and are compulsive liars. They can either want a lot of friends, or none at all. They often seem like two different people, depending on their mood. They fear being trapped. Sometimes, they'll get depressed for absolutely no reason at all. Torn Angels often end up becoming psychopaths or mental patients. They are often drawn to potential friends that highlight both sides of their personality.
I think it's quite precise on my personality.
Outside Context Problem: If there is one villain no one was expecting, it would be you during a genocide run. An interdimensional Humanoid Abomination, out to destroy the underground, come on?
Omniscient Morality License: Since you have the ability to go back and fix things whenever you want, just like any other video game, it's completely fine for you to take any innocent life you want, right? Wrong.
Sans: sometimes... you act like you know what's gonna happen. like you've already experienced it all before. this is an odd thing to say, but... if you have some sort of special power... isn't it your responsibility to do the right thing?
No
Sans: heh. well, that's your viewpoint. i won't judge you for it. ... r.
Pay Evil unto Evil: You can take the game's story and characters 100% seriously and still choose to kill some of the more aggressive monsters if you think they deserve it.
The Perfectionist: If you're trying to do a specific playthrough yet reset or save scum after every screw-up. Flowey may even call you out on it depending on the circumstances.
Person of Mass Destruction: As Sans describes it, the No Mercy path will not bring you any kind of satisfaction, you'll just keep consuming timeline after timeline.
Player and Protagonist Integration:
You start controlling Frisk as a Heroic Mime, and in most playthroughs, that is all that you are. Only Flowey knows that you're not really Frisk. By the end of each route, it's clear you're separate entities: either you are playing as the Fallen controlling Frisk, or as yourself wrestling for control from the Fallen (or controlling both of them as The Corrupter).
The distinction between you and the First Child is vague to say the least: although the First Child takes the name you give them and is a dark take on the behavior of a Club or Diamond kind of player, they clearly become their own person if you let them get their way. They consider you their pawn and on a second Genocide ending find it curious how you wish to recreate Undertale over and over to toy around with its people even at the expense of your soul — a different flavor of depravity than their own.
Reality Warper: You can delete and edit the game's files, which clearly makes you this in a meta way, and, as said everywhere else, Undertale is a very meta game on purpose, then there's the ability to reset.
The Sacred Darkness: Instead of being the Dark Side, you can choose to be this if you play pacifist. In pacifist while still being an Eldritch Abomination, you are good and save everyone. This especially if you believe you're the darkness Gaster saw.
Sadist: You can be this if you enjoy hurting or killing your enemies or fake sparing them.
Satanic Archetype: Just look at the other tropes, especially for the genocide run, a sociopathic, sadistic and ax crazy Ultimate evil Greater Scope Villain Eldritch Abomination motivated For the Evulz, You even got your own Antichrist working for you in all routes.
Sentient Cosmic Force: An interpretation, you're a being only visible in consequences that happen in the timelime, you are the driving force in the world, it could be said that you are Frisk/Chara's DETERMINATION.
Set Right What Once Went Wrong: Should you ever have a change of heart during the Genocide route, undoing your mistakes via a Reset is always an option. Once the route has been brought to completion and the entire world has been erased, however, you'll have no choice but to live with your mistakes.
Slasher smile: I don't know about you other players so it's YMMV, but I personally [AxCrazy/have been making quite a few of this] in my [Kill 'emAll/No Mercy run].
Stupid Evil: The Genocide route is emotionally exhausting, makes you feel like a complete and total monster the entire time, is chock full of tedious Level Grinding, forces you into situations where you will need to grit your teeth and persevere in order to continue despite resetting always being a viable option, and permanently messes up your game so you can't get the Golden Ending ever again. So why would you even think to do it? Oh yeah, that's right... because you can.
Sans: and because you "can"... ...you "have to".
Symbiotic Possession: The player controls most of Frisk's actions, but a more benevolent player acts closely to Frisk's desires anyway. As Frisk is a child, they arguably couldn't complete their quest without you even if they could use determination on their own.
The Soulless: You sell your soul to the Fallen Child after a genocide run in order to restore the world, though from Chara's comments, it seems like you're still connected to it as it resonates your feelings even after you've lost it.
The Sociopath: In the Genocide run. Selfish, unfettered to get what you want, extremely sadistic and violent, [LackOfEmpathy/ shooting down any mercy or remorse], unrestrained by fear or compassion, driven solely by an impulse to do it(possibly due to a need for stimulation), completely uncaring of the characters do to it being just a game (notice that I'm talking about genocide player seeing it as a game with characters rather than a world with living beings), complete disregard for any possible consequences and many experience mood swings in Let's Play or without them to boot. You are one of the big examples of a low functioning sociopath for videogames in general in this run, along with Chara (who's more high functioning) and Flowey.
Super Powered Evil side: For Frisk, especially when you start killing people against the loving pacifist will (especially in no mercy), remember, Frisk is just a little kid who most likely would have died in their journey's first steps. You're the one fighting, the one dodging and the one killing. In pacifist you're a lot more benevolent Super Powered Alter Ego. In an extremely confusing double whammy, the fallen child is also this to you, they're everything destructive and terrible you've done in a videogame come to life and barely even exist or do much more than talk if you don't provide them with ample LOVE. They could also be this for Frisk.
Soft spoken Sadist: I watched many Let's Play on a genocide run and I'm currently on one myself as I'm writing this, there isn't much rise of volume, even with most mood swings.
Time Master: In this game, reseting and reloading are real, In-universe things.
Talk to the Fist: On the Genocide path, you often walk up to the major characters and one hit-kill them without a word.
The Unfettered: Undertale is heavy on meta commentary about how your actions can affect the game's world for the worse, what might be your reasons for pursuing bad outcomes and even how much you're willing to cheat to take what you want from the game. If the worst comes to pass, Sans accuses you of having done it all just because you could and the Fallen Child outright calls you the sort of person who thinks themselves to be above consequences and who acts on perverted feelings for the game's setting. You can prove that and assert your power over the game by erasing the extra files that record your deal with the Fallen. On the other hand, there are plenty of people out there who have resisted the temptation of doing a Genocide run and who even hesitate in doing a True Reset after listening to Flowey's last request.
Ultimate evil: Being the player, you're of course never seen within the game, in fact, almost no one knows who you really are.
Villainous B.S.O.D.: A very, very common reaction - the intended reaction, even - for those who play the Genocide route, especially those who had no idea what they were getting into. Some choose to Reset and undo their mistakes at that point, while others choose to grit their teeth and press on anyway.
Well-Intentioned Extremist: You can invoke this (especially if this isn't your first playthrough) as an excuse to kill every boss monsters while sparing the citizens. This results in the Annoying Dog taking over the throne, and arguably the second best ending in the game right after True Pacifist. Even Sans would say thanks at the end of it, despite him being rightfully angry at you killing his brother earlier.
What the Hell, Hero?: Beating the game on the True Pacifist Run and restarting the game gets you a lecture from Flowey of all characters, calling you out on taking the characters' happy ending away from them because you were bored, and referring to you as a worse person than him.
Wrong Context Magic: Even if it's only a few people, there are those who know about the power of Determination and resetting. What they don't know about is the Anomaly's power to alter the game's code. Even Chara's attempts to trap them with the consequences of the Genocide run are nothing in the face of this.
Yandere: You can be a platonic version of this if you Reset a true pacifist ending, taking away a happy ending in order to expend more time with characters you´ve grown to love.
Yank the Dog's Chain: How the aforementioned permanent Heel–Face Door-Slam manifests. Even if you do everything right and get a Pacifist Ending, in the end, the Fallen Child is revealed to still possess your soul, after which they'll possess Frisk and kill everyone again, anyway.
Your Approval Fills Me with Shame: Just like My God, What Have I Done? trope above, the game evokes this trope to the player at its hardest. When Flowey or Chara/The Fallen Child congratulates you, the player for killing Asgore and/or Flowey himself in the Neutral route on the former, and completing the Genocide/No Mercy route on the latter.