Spoilers from included and/or represented works abound. Please read this fiction carefully.
The very fight, between the alliance formed by Shinra and Ouma, including the Seven, the Cube Queen, the Hegemonies, and many others, alongside Goku, Vegeta, their fusions, Ichigo, both versions of Naruto, and both versions of Sasuke, all against the fusion of the false Director of J-Force and the Evil Omni-King, wearing the extreme Ultron armor and bolstered by the Black Lanterns, Sigma Virus and three full sets of Infinity Stones... got intense and body from the very first successful hits. The alliance used their powers, abilities and skills creatively to trades blow with the fused man. David and Smasher even used Sandevistan and assisted any strikes they could possibly augment.
All just under the Pyramid.
"Multi-go!" Multi-Attack, made by Reiji, Xiaomu, Saya, Kogoro, Mii, Haken, Kaguya, Due and Meden.
"Oros Phlox, charge ahead!" The Oros Phlox joined the fight to assist the alliance.
All the mecha pilots except Haken went to their respective mechas and fired bountifully towards the Daikaiser. The latter countered by throwing the mechas out, though they simply flew out and back.
"You piece of spark!" The Ouroboros Interlinked and bombarded Prometheus.
Zanza and Meyneth took their Monados and directly striked at Prometheus.
"I hope it isn't all what you've got!" Prometheus countered, knocking both gods away.
"Hey, Klaus!" Steves Roger threw his shield to Zanza.
"Take the shield then go throw that out without even giving him the chance to think!" Captain Carter gave her shield to Meyneth.
Zanza and Meyneth took the shields, looked at each other briefly, and then flew around and threw the respective shields, catch to exchange the other shields alternatively, and threw, then catch to exchange, and threw and catch other... repeat, while slashing afar with their respective Monados.
"Shoot!" Several used firearms to shoot Prometheus.
Ending up with Zanza and Meyneth return the shields to their respective owners and simultaneously slash Prometheus with Monados. Prometheus followed by throwing both gods away.
"Shinkuu... Hadoken!" Ryu fired the Shinkuu Hadoken, which Prometheus then blocks with his bare hand...
Only to Goku, Vegeta, Gogeta and Vegito fire their Kamehamehas in the behind, blasting off the Daikaiser.
"Damn!" Prometheus then tried to stand up, but is strangled by Shuma Gorath summoned by Strange Supreme.
"Don't you dare escape!" Thanos then stabbed Prometheus, but the armor blocked it without problem. "What?"
Prometheus pulsed using the Power Stones, knocking both Shuma Gorath and Thanos away. David approached with Sandevistan, and headshot Prometheus an Thudaga-charged projectile.
"Hmph." Prometheus is unfazed. He then tried to punch David, but the latter evaded and went behind.
"Tenzai Ninjutsu on steroids!" Kogoro used the Super Star provided by SMG4, and then bombarded with his ninjutsu.
Prometheus then stood up and withstood the ninjutsu without much effort, then teleported to above.
"Damn it!" Kogoro is frustrated, and Super Star's effect expired.
Prometheus appeared above, just in the height like Susanoo and Kurama.
"I shall bring death to you!" Ichigo proceeded to strike Prometheus.
"Infinity Themis."Prometheus creates two white orbs that fire Infinity-Stones-powered lasers at the opponent. It fired at Ichigo, who barely dodged.
"Unbelievable!" Ichigo just dishes, but his arm is then grabbed by the Daikaiser.
"You'll regret defying me." Prometheus is about to fire a laser at Ichigo from the Mind Stone on his forehead. "Say bye."
Young Sasuke then shot Indra's Arrow at Prometheus. Theatter simply catched it with his bare hand. Ichigo took advantage and slashed Prometheus and ignited the arrow, exploding the latter and knocked the Daikaiser off, freeing the Hollow-Quincy Substitute Shinigami.
"Bite!" Luffy then took advantage of Gear 5: stretching his neck to catch Prometheus, then bite the Daikaiser.
"Spin!" Prometheus then sounds good body, pulling Luffy into him, allowing him to catch and grab the pirate. The Daikaiser then landed down, but Lucy escaped in the process.
Then the adult friends, Naruto and Sasuke, both ended up facing Prometheus.
"All worlds are in danger because of Empress Zero's meddling." Naruto told Prometheus. "I got those infos from being client of Shinra few days ago."
"Care to explain?" Sasuke asked Prometheus.
"Firstly, Empress Zero is right." Prometheus told why. "Secondly, I will have revenge."
"Finally... I can become a god." Prometheus concluded.
Naruto and Sasuke then wasted no time doing Rasengan and Chidori respectively., then they combined those and charged towards the Daikaiser.
"Rasen... Chidori!" Naruto and Sasuke then put that at Prometheus, causing electric-wind explosion and knocking the Daikaiser away.
"Argh!" Prometheus is driven away.
"Now!" Naruto told the Hegemonies and the Investigation Team.
"Persona... go!" The Investigation Team turned their main Persona into their ultimate forms: Izanagi-no-Okami (for Yu), Susano-o (for Yosuke), Suzuka Gongen (for Chie), Amaterasu (for Yukiko), Dairoku Tenmaou (for Kanji), Kanzeon (for Rise), Kamui (for Teddie) and Yamato-Takeru (for Naoto).
"I see you. I see your Persona." Prometheus noticed the Personas.
"Don't!" Mitra, Magsarion, Hajun and Hirume striked with their mights, on all sides.
"Argh!" Prometheus for hit by them, getting stunned.
"Dura Lex Sed Lex!" Mercurius creates a Great Attractor onto Prometheus, pinning the Daikaiser with abnormal gravity that would otherwise crush anything.
"Hgh!!!" Prometheus struggled to break out.
"Can you handle it?" Mercurius then casted Aurea Mediocritas: aligns the stars into a Grand Cross, causing an astrological energy surge that can incinerate a Hegemony God from inside-out... that, at Prometheus, burning the Daikaiser.
The Investigation Team took advantage and striked at Prometheus. Many of Shinra agents' old friends (who ventured alongside Reiji and Xiaomu during Ouma's plans and Oros Phlox's tenure) also joined as well, as does the S.E.E.S., who summoned their Personas.
"Hit them with all our might!" Mitsuru, having summoned Artemisia, told S.E.E.S. members and the Investigation Team.
"Got it, Mit-chan!" Teddie agreed and charged ahead.
Yukari readied her persona Isis, while Ken Amada (with Kala-Nemi) and Koromaru (with Cerberus) tagged up real quick.
"Now go!!!" Junpei Iori, with help from Persona Trismegistus, hit Prometheus Daikaiser.
The Investigation Team, members of S.E.E.S., the Hegemonies and various of Shinra's friends then striked alternatively and continuously at Prometheus while he's burning with the compressed surge of energy pinning him which prevented the Daikaiser from independently moving. The Daikaiser himself struggled to free himself out, and is bombarded by so many. Not long after, Sora, Roxas, Mickey Mouse and friends also joined as well, with Ultima and Two Becomes One and the Oathkeeper-Oblivion combo working wonders.
"Argh! It hurts!" Prometheus is being tortured.
He struggled and fended off the Cross and over-gravity, ultimately and finally free himself.
"No escape for you!" Reinhard then threw his Lance of Longinus, stabbing the Daikaiser from afar.
"Die!" Ragna and Hyde went for Astral Heat/Infinite Worth (Black Onslaught and Gyre Vortex Raging Roar) at the Daikaiser.
"Super... Vivas Las Vegas!" The alternative Thor and Earth-616's Janes Foster, the Mighty Thor, then both summoned lightning at Prometheus with their Mjonirs.
Followed by David jump-boosting and shooting Prometheus with Rebecca's shotgun, then finally...
"It's over, Prometheus! Zarathustra!" Ren Fuji, as Tenma Yato now, quickly decapitated the Daikaiser.
Prometheus exploded, seemingly dying taking off the Crossing Wasteland...
Prometheus rewinded and create a pulse that created a temporal bubble powered by Time Stone, pushing all the nearby foes away.
"Margueritte Bois de Justice, as long as that curse can make contact with the target's neck, one can permanently and over-kill anyone through immediate decapitation." Prometheus commented, while he started floating again and up. "However, with the blessing from Empress Zero and the Infinity Stones, I have since gained nullification of that annoying curse." *collapses faceplate*
"Therefore, your decapitation blade has no real effect on me. Thus, I rewinded and busted you." Prometheus told Ren Fuji. "Got you, Zarathustra Ubermensch!"
Prometheus floating up, and the alliance outside of the temporal bubble is shocked.
"That's beyond impossible!" Deadpool is shocked. "Marie's curse is supposed to end a person's live forever! How did he no-sell that!?"
"My curse has no lasting effect on him whatsoever!?" Marie is shocked and frustrated at Prometheus' survival. "Who you even are!? And why!?"
"I told you, Margueritte Breuil." Prometheus responded to Marie. "With the blessing from Empress Zero and the Infinity Stones, I have gained nullification of your annoying curse."
"Bullshit!" Nero facepalmed.
"Makoto Yuuki. Kotone Shiomi. Angela from Lobotomy Corporation. Kamen Rider Ginga. All rise." Prometheus decided to summon Makoto Yuuki, Kotone Shiomi, Angela/Carmen and Kamen Rider Ginga.
Strange Supreme saw it all, and he swallowed a Soul Stone previously used against Xenohanort, and activated the Time Stone used in his wake.
"Awaken!" Supreme then quickly summoned Shuma Gorath and caught Prometheus.
The temporal bubble broke, leading to everyone who's caught on it to stop momentum and fall down.
"How dare you, the Sorcerer Supreme!" Prometheus is frustrated.
The Daikaiser then briefly waved his hand, then telekinetically stole Thor's Stormbreaker.
"Oh crap!" Thor is frustrated as his Stormbreaker flew towards Prometheus.
Supreme then casted a spell to clone out Stormbreaker as to overwhelm the Daikaiser, much like during Infinity Ultron's genocide (when alternative Thor's Mjonir got duplicated by the same spell). The Stormbreakers ended up surrounding and burying Prometheus.
"Mighty Thor, now!" Junpei Tenmyouji shouted. "Taion, cover that with Mondo!"
"Ok!" Mighty Thor them summoned lightning to the Stormbreakers, while Taion took his Ouroboros form and summoned a massive lots Mondos to cover the Stormbreakers. The lightning quickly detonated Mondo, and the whole ball exploded hard.
"Good play!" The main Thor then retrieved his Stormbreaker from the explosion... but the momentum pulled him far onto the way, crashing into team Baku.
"Ugh! Damn way!" York falls down.
"Mister, be careful..." Miko is dizzy. "Ow..."
The smokes subdue, revealing...
"You're impressive for a bunch of lowlifes." Prometheus commented.
"How...!? He couldn't have survived that!" Vegeta is then enraged.
"You shall be exterminated!" Prometheus then summoned several copies of Infinity Ultron's double-headed spear, and have them fire the energy of the Black Lanterns at the alliance.
"Dodge and bust!" David told everyone.
The alliance tried to dodge the Black Lanterns' rays, leaving now wreckage in process.
"Captains... Marvel! Take down those!" Sheath forced Carol Danvers, the Captain Marvel, and Billy Baston as Shazam.
Captain Marvel and Shazam proceeded to destroyer the spears, while Klonoa and SMG4, both running with Super Star, distracted the Daikaiser.
"Be killed." The remaining spears then flew towards Ren Fuji.
"Your don't!" Ren Fuji created a time-stopping shield to protect himself, stopping the spears from contact and desiring all those remaining ones.
"You like an all-piercing spears stabbing against an unbreakable shield?" Ren Fuji made fun of the Daikaiser. "Nice try."
"How did you pull that so-last-tenure trick from when you went against Māra Papiyas?" Prometheus is surprised at the trick.
Ren Fuji gathered the blades on him into his usual decapitation blade as on his right arm.
"No, Mr. Tenma Yato!" Lucy warned Rem Fuji. "Don't you realize that you cannot kill him by decapitating him?"
"If the head isn't valid, I'm gonna aim at the Infinity Stones!" Ren Fuji then charged ahead.
"Even if you manage to shatter any Infinity Stone on me, I can fix it immediately without problem." Prometheus told Ren Fuji. "Therefore, your trick won't work."
At this point, Ren Amamiya pointed gun alongside his ultimate Persona, (Archangel) Satanael, towards Prometheus in the back, at point-blank.
"Phantom Thieves of Hearts send our regards." Ren Amamiya pulled the trigger.
The shot didn't affect or faze the Daikaiser at all. He looked back towards the Joker, glaring at the main.
"You have some funny changes indeed." Prometheus commented.
"Joker! He shrugged off that ultimate bullet!" Morgana is shocked.
Prometheus turned back and pushed Ren Amamiya away, but Lucy and Sophia restrained the Daikaiser with her monowires and her yoyo, respectively. The rest of the Phantom Thieves then shot the Daikaiser again, as does members of Oros Phlox.
"Full-force fire!" The Belanos duo shouted.
"Everyone fire at this chrome-plated monster!" David froze Prometheus and brought Lucy and Sophia away from that.
The mechas pilot fired their arsenal again, at Prometheus. The majority of the alliance did the same as well, both physically (with firearms and the likes) and magically (through spells). Even Mercurius made a rain of meteors to the Daikaiser.
Which ended in a lot of holes around and under the Pyramid.
"Did we do it?" The Cube Queen is curious.
"I don't see him anymore." Star Lord doesn't see any of Prometheus.
"We won, right?" The alternative Thor then?
"If so, then that's so cool!" Main Thor exclaimed.
The smoke settled and slowly went off, and the silhouettes of Makoto, Kotone, Angela, and Kamen Rider Ginga.
"Wait... Angela!?" Nerose Satanael is shocked. He took off Angela's book in surprised.
"What? Our friend is..." Akihiko Sanada (with Caesar) is surprised.
"Is that... the-" Futaba recognized Kotone.
"It's two people who sacrificed to seal off Nyx." Professor X revealed. "Those two were from two different timelines, in the exact same place as the leader of you, S.E.E.S."
"You mean they're..." Aegis shooked her Persona, Athena, and is surprised.
"And most importantly..." David recognized Kamen Rider Ginga. "Kamen Rider Ginga!?"
"Wow, that was quick." Angela then looked at Nerose Satanael. "Wait... my books..."
Angela then ran towards Satanael because he has her book.
"Found you!" Angela then snatched the book from Satanael. She then casted a spell to knock him away.
"What!?" Satanael is frustrated. "You sinner want to do with us?"
"You arrested me because I believe in Empress Zero!?" Angela asked.
"Don't you see? Empress Zero caused too much damage to the omniverse!" Magsarion responded to Angela. "Even Hajun, the extreme evil besides me, is absolutely disgusted by her mere presence!"
"You made no peace." Hajun pointed it out.
"She broke the omniverse, and you support her!?" Hirume asked Angela.
"What's going on? I was against Nyx..." Makoto Yuuki is confused. "Me sealing and smiling for the S.E.E.S., now someone just..."