Sans truly hated Frisk, and Frisk accepted that. This was all her fault after all, just not in the way that he thought. The power of RESET was Frisk's and Frisk's alone, although she could only reset at the 'End'… The rest, however, Chara had all the power.
Chara's actions were also Frisk's fault, but Frisk truly had never meant for any of this. During the first timeline, Chara had remained a quiet observer all the way to the end, never interfering. After Frisk had brought the monsters back to the surface, she noticed that she had access to an option she had never had before, RESET. She had honestly lasted longer than what was expected in avoiding the temptation, but eventually, curiosity got the better of her and she RESET.
That was Frisk's sin, the sin that had caused so much misery. While Frisk returned back to the beginning with her memories fully intact, Chara's did not. Whether it was because of Chara's strange connection to Frisk or something else entirely, Chara's memory seemed to have become corrupted, unable to tell what was her own memories and what was Frisk's. Frisk reasoned that Chara must have seen the monsters' attacks on them as a painful betrayal, unable to tell that they were actually aimed at Frisk rather than their now dead friend. Chara took control over Frisk's body to get revenge in the form of the first genocide run for their so-called betrayal.
Frisk was given no choice again and again just to wait everything out and RESET at the End hoping for the chance that Chara might give the monsters MERCY in the next run, but things only got worse with each RESET as Chara got more and more demented. Frisk's self-loathing of herself for causing all of this began to creep into Chara and Chara's hatred shifted from the monsters onto Frisk herself, until the point that this was all one big game to torment Frisk. Chara would even give control back to Frisk from time to time, allowing her to SPARE some monsters, only to take over again and dust the rest. One time even, they had allowed Frisk to go all the way to the End, letting Frisk SPARE everyone and bring them back to the surface, only to kill them all there, forcing Frisk to RESET once again.
It was sometimes easy to forget that Frisk was just a kid, only twelve years old, and this was taking a toll on her. As horrible as it was, seeing her friends die over and over wasn't the worst thing anymore, but Sans no longer even hidden contempt towards her, even when she was in control, that, was the worst. She wanted more than anything to plead for his forgiveness but she still hadn't been given the chance to give Sans an explanation.
Chara had made it again all the way to the End of a genocide run, and the child and the 'demon' stared at each other in the pitch black darkness staring at each other; Chara in a mad glee and Frisk with cold, dead eyes. She was taking her time to RESET, she was so tired, and didn't know what Chara would do on the next run.
It was sick, Frisk had gotten to the point that she almost dreaded the times that Chara let her have control because she hated letting her hopes only to have them crushed again. Chara's cruelty was bound only by her imagination, and she had quite the imagination, she would always take over once Frisk developed any sense of security; while she was saying goodbye to Toriel, halfway through her first encounter, when she was sparing Asgore, Chara had even once allowed Frisk to take over mid-way through a genocide run and SPARE Papyrus, only to stab him in the back while he was hugging the wailing child.
Frisk slowly raised her hand, bringing the RESET button into existence, she stood a while, not pressing it just staring. Chara chuckled sadistically. Frisk moved her hand to press it when she suddenly sensed another presence here when it had only ever just been the two of them. Frisk looked up to Chara, who was also disturbed by the presence, this shouldn't have been possible, all of reality had been ERASED, only they existed now, but still, the other presence was undeniable, they both felt a thousand eyes stare at them.
Suddenly, out from the darkness, a smooth, feminine voice spoke, drawing both children's attention, "I have a proposition for you, child." They had a human figure, but they were obviously not human, their skin was grey, and not as in a sickly dead-body grey, but an actual grey. Their eyes instead of having a colour like blue or brown were black, so you couldn't see their pupils - or maybe they were all pupil - surrounded by the glowing whites of their eyes. She -at least Frisk thought that they were female- had blood-red hair that was long and messy, like they hadn't bushed their hair after waking up, but they wore a formal business suit, only with a red undershirt instead of a white one.
Seeing Frisk's stare the figure grinned, revealing her black teeth and making Frisk's eyes widen in fear, "What, child? Have you never seen a demon before?" The demon asked. Frisk's eyes unconsciously went to Chara. Although she knew that Chara wasn't actually a demon, after everything she had begun to call her one in her head. Chara had remained quiet as always, but now a jealous snarl was on their face, like a child who saw someone stealing their favourite toy.
The demon continued talking, "Well you have no need to fear, I'm not going to hurt you, after all, I did come here to strike a deal with you." Frisk eyes went back to the demon wide in fear, she had heard stories of those who had made deals with demons, and they all ended badly for the fool who had excepted the deal.
The demon chuckled, "Relax, for I am a demon of mercy." She spoke smoothly, like a mother comforting a child. "I work as a demon under the great sin of Sloth, I free man of the harsh trials of this world, for a price of course. And now I am offering that to you, to take you away from this never-ending cycle of torment, so you never have to see your friends die again."
The words were exactly what Frisk wanted to hear, and although she knew that was what the demon was counting on, there was not much strength of will left in Frisk, and so she let her worries fly away, and listened contently to the demon, letting them become her saviour.
The demon smirked, knowing that she had already won, but continued, her tone never changing. "Your problem lies in that human soul of yours, its power leaves you with too much responsibility for a young child like you, it gives you the strength to destroy monster kind over and over again, while allowing you to be controlled by the corrupt," The demon sent a glance to Chara, allowing them to see her smirk. "I just want to take that soul off your hands, I'll even give you a discount and give you a brand new one, only it'll be a monster soul, free from your current soul's power and problems."
Frisk hesitated unsure, looking down, the deal sounded so good, but still, her soul was needed to free the monsters wasn't it, and more importantly, with a monster soul she wouldn't be able to SAVE anymore, with her human body it was very likely that she would be killed in the underground before being able to make up her past mistakes to all the monsters she had hurt in previous timelines.
The demon sensed this and continued. "A monster soul, would, of course, have to come with a matching monster body, you could be any monster type you wanted, Froggit, Fire Elemental… Skeleton," Frisk looked up at that, causing the demon to chuckle once again, "Skeleton it is. Come on Frisky, what do you say?"
Chara watched in anger and horror as Frisk nodded.
"Deal."
