Here's a trailer to welcome the MCU along with the ones from the DC Universe. It's here at the last day of the year; also after passing 4 years, I finally overcame the Thanos' Snap scene in "Avengers: Infinity War".

Marvel Cinematic Universe: Joint Dark Energy Mission Facility

Just before the events of "Super Smash Bros Kombat Z"; in a distant world a group of scientists were working on the Project P.E.G.A.S.U.S, two persons were watching the situation with an item called Tesseract until it opened a portal which came out Loki, the brother of Thor who is holding a scepter.

"You have heart." Loki said before putting Clint Barton under his control.

Nick Fury and Maria Hill tried to stop Loki, but their attempt was in vain, Loki stole the Tesseract and the facility was destroyed. Now Shield was at war.

Loki's Hideout

But Loki and the Chitauri won't be alone. He meets Bowser, Bowser Jr, Queen Beryl, Lord Ozai, Azula, the Koopalings, Kamek, the Psycho Rangers, the Phantom Blot, Dr. Eggman and his seven robots, Metal Sonic, Giovanni, Matori with the Alolan Meowth, the Black Tulip, Team Rocket, Cassidy, Butch, Team Monty, Ganondorf, Lord Nightmare, Lord Zedd, Rita, Rito, Goldar, Scorpina, King Mondo, Queen Machina, Prince Sprocket, Oogie Boogie, Lord Dragaunus, Siege, Chameleon, Wraith, Lord Voldemort, Malfoy Family, Death Eaters, Dolores Umbridge, Jafar, Maleficent, Ursula, Dr. Facilier, Yzma, Lady Tremaine, Hades, Merlock, Magica De Spell, Madam Mim, Horned King, Zurg, Gargamel, Azrael, Monty the Vulture, Cozy Glow, Chrysalis, Tirek, King Sombra, Grogar, Megatron with the Decepticons, Shredder, Aku, Dr. Cortex, Uka Uka, Winterbolt, Negaduck, Megavolt, Bushroot, Liquidator, Quackerjack, Red Claw, the League of Villains, Grandmaster Meio, Dr. Wily, Vile, Gemini Spark, Jedah Dohma, Vergil, Wesker, Shang Tsung, Tanya, Rain and Goro.

The new ones in the Brotherhood of Evil are Dr. Doom (Four Fantastics 2000's appearance), Sabretooth (X-Men Movies' appearances like the others three), Juggernaut, Silver Samurai, Madame Viper, Aleksei Sytsevich (The Rhino from Amazing Spider-Man 2), Lex Luthor (from DC Extended Universe like the others 3), Cheetah, Deathstroke, Joker, Captain Cold (Arrowverse's appearance), Bane (Nolanverse's appearance), General Grievous and Count Doku.

"Believe that S.H.I.E.L.D. is not the only threat in this world." Bowser explained to the God of Mischief.

"Beyond this world there are a lot of heroes." Maleficent explained before showing the projection of Caleb along with the other heroes.

"Together we'll assist you to defeat them." Grogar told him.

"Very well." Loki agreed to join forces with the Brotherhood of Evil along with the Chitauri too.

Helicarrier

Inside the giant air vehicle, Nick Fury was speaking with the High Council of Mentors (an alliance with people from different worlds which will appear through the series).

"This is out of line, Director. You're dealing with forces you can't control." The Grand Councilwoman told him.

"You ever been in a war, Grand Councilwoman? In a firefight? Did you feel an overabundance of control?" Nick Fury asked her.

"So, you're saying that this Asgard has declared war on your planet?" Kit Cosmos asked, referring to the world from the Nordic mythologies.

"Not Asgard. Loki." Nick Fury corrected him.

"Loki?" Yamaki repeated, never hearing that name.

"So, he managed to survive his fall." Master Yen Sid said.

"I'm afraid so, Master Yen Sid." Nick Fury told Mickey's mentor.

"Fury, my sensors tell me Bowser must've met Loki. So he can carry out his plan." Zordon explained to Nick Fury.

"Then it's true. The Ultimate Battle is coming." Millennium Star said.

"Indeed. But they can't be working alone. What about his brother?" Princess Luna asked, referring to Loki's brother.

"Our intelligence says Thor is not a hostile. But he's worlds away, we can't depend on him to help. It's up to us." Nick Fury explained to the Equestrian Princess of the Moon.

"Which is why you should be focusing on phase 2, it was designed for exactly…" The Grand Councilwoman was saying.

"Phase 2 isn't ready, our enemies are. We need a response team." Nick Fury explained to her.

"Yes, it's up to the Super Smash Brothers team." Millennium Star said.

"Despite the Keyblade Bearers looking younger, they are so skilled." Master Yoda said.

"Yes, but my only concern, Fury, is that your Avengers Initiative did got shut down by the world security council." Merlin said.

"This isn't about The Avengers." Nick Fury told Arthur's tutor.

"But it may be dangerous for the Digidestined. Even though they have defeated Bowser and his forces of darkness several times." Fairy Godmother said.

"Yes, but since Zordon's prophecy is coming true. It would mean that those heroes are growing into a giant army." Princess Celestia before thinking in concern about Twilight Sparkle and Aria, both human girl and alicorn are two daughter-like figures for the Equestrian Princess of the Sun.

"Precisely. But Fury, if you do have the Super Smash Brothers join these Avengers of yours that would mean…" Zordon was explaining.

"That I know Zordon. But we need a response team. These people may be isolated, unbalanced even, but I believe with the right push they can be exactly what we need." Nick Fury explained Zordon.

"You believe?" Zeus (Disney) asked.

"War isn't won by sentiment, Director." Colonel Campbell told him.

"No, it's won by soldiers." Nick Fury said, meaning it is time to recruit another ally.

Then in Solenski Plaza in Russia, Natasha Romanoff or known Black Widow, received a call about Barton's life in danger, then she managed to defeat Georgi Luchkov and his subordinates.

In Kolkata, India, Black Widow meets Bruce Banner, better known as Hulk.

In New York, in a boxing gym, Steve Rogers or known as Captain America, was punching a sandbag while flashbacking memories from the past (events from "Captain America: The First Avenger") until he re-meets Nick Fury.

In Stark Tower in New York, Tony Stark or better known as Iron Man, after obtaining clear pure energy for Stark Tower, he celebrated with Pepper Potts until they were interrupted by the agent Phil Coulson to tell Stark about the Avengers Initiative.

In Baxter Building from New York, Phil Coulson arrives to meet the Fantastic Four.

In Pym Residence, in San Francisco, California. The Digidestined team along with the other heroes (OCs too), they meet Maria Hill and later she tried to recruit Hank Pym, but he told her that he can't because he lost someone important and wasn't disposed to join the Avengers Initiative, but he meets someone.

In San Quentin State Prison, California, Scott Lang was there until his bail was paid, his cellmate Luis was there too.

"Hi Grubber!" Pinkie said greeting, but at Luis, probably she must have mistaken his voice.

"Does anyone know the pink pony?" Luis asked.

(fun fact: Michael Peña who portrayed Luis in Ant-Man, he voiced Grubber in My Little Pony: The Movie)

In New York Sanctum, Doctor Fate arrives there where he meets the Ancient One.

In Westchester, New York, in a building called X-Mansion, Professor X felt the death of some mutants in the Mojave Desert in Nevada due the explosion in the research facility. Then he calls Wolverine, Cyclops, Storm, Rogue, Nightcrawler, Iceman, Archangel and Colossus where they meet Nick Fury.

Later in the streets of Westchester, Nick Fury meets Deadpool.

"I know you have a record of killing criminals, arms dealers, murderers, yakuzas, including Francis Freeman, but we need your help to…" Nick Fury explained.

"I don't want to interrupt you, but I still have the proposal to join the X-Men, and besides being a hero is not my thing, they always respect the law." Deadpool explained to the Director of S.H.I.E.L.D.

"Part of the X-Men are part of the Avengers Initiative." Nick Fury replied.

Deadpool gasped while putting his hands in the cheeks from his red suit before staring at the readers/viewers.

"For the fans who wanted to see me in The Avengers, this is going to be good." Deadpool said, breaking the fourth wall, then he turned to see Fury. "Count me in."

In Vienna International Centre of Austria, Professor X arrived to meet King T'Chaka and his son, Prince T'Challa.

In another part of New York, Peter Parker or Spider-Man (Andrew Garfield: Earth-120703) arrived there.

Also, Gwen Stacy or Spiderwoman arrives in New York.

The League of Justice (Superman, Batman, Wonder Woman, Aquaman, Cyborg, Flash, Green Lantern or Hal Jordan) arrived in the city too.

In the Comet Observatory, the Silver Surfer was in the Gateway until he woke up and watched his surroundings.

Green Arrow, Black Canary, Night Wing, Red Hood, Hawkman, Atom, Captain Marvel (DC; or Billy Batson), Beast Boy, Firestorm, Spawn, Starfire and Robin arrived in different parts of New York.

Daredevil, Punisher, Namor the Sub-Mariner, Captain Marvel (or Carol Danvers) and Ghost Rider were recruited too.

In the fields, Raven launched Twilight against a boulder, the alicorn has a lot of scrapes and cuts in her body and coughed blood, just before Raven could strike her, Aria appeared and performed Thunder Strike before using Ragnarok to hit Raven sending her away from Twilight.

"Don't you dare to hurt my sister like that again!" Aria shouted with a threatening tone at Raven.

Then she approaches Twilight before hugging her.

"Are you okay, Twi?" She asked her with concern.

"Yeah, thank you." Twilight said but suddenly she winced in pain from her injuries.

"Twilight…" Aria said with concern, but she decided to cast Curaga to heal the alicorn's injuries. "I couldn't let them hurt you again, you're one of my best friends."

She hugged her again tightly without suffocating her, then Twilight returned the hug, but suddenly they heard Raven reappearing again with energy yet, both separated themselves from the hug.

"Aria, stand aside, I will handle her." Twilight told her human sister-like figure.

"No, we got this together." Aria told her with a confident smirk and Twilight nodded with a confident smirk too as both were facing Raven.

In Stuttgart, the capital of the state of Baden-Württemberg in southern Germany, Link, Caleb, Luke and Sora were fighting against Loki. Then in the battle, Anakin and Obi Wan joined the battle.

"Hello there." Obi Wan said to the God of Mischief.

During a battle in New York City, an explosion occurs causing to fall down as she was screaming.

"Sara!" Luke shouted at her sister.

Then Spider-Man arrived and managed to rescue Caleb's twin sister while also getting over the scene from his past (the one where Gwen Stacy dies in The Amazing Spider-Man 2).

"Are you okay?" Spider-Man asked her.

"Yeah…" Sara asked a bit shaken before being put in the ground before hugging Luke tightly and streaming some tears of fear after passing for a near-death experience.

The heroes were fighting against the villains and the Chitauri army too, even Venom (Sony's Marvel Universe) joined the fight who managed to defeat some Chitauri.

"What the heck is that thing?" Wolverine asked in shock at the sight of the alien-like creature.

"We… are Venom." Venom and Eddie Brock said together before resuming in the battle.

Sanctuary

Meanwhile in a place in outer space, two figures watched the events of the battle.

"So… Ronan failed in destroying Earth previously, just like Stepphenwolf failed in destroying Earth where I come from, and now Loki has failed his mission." Darkseid said before asking. "Shall I take care of the Justice League and those so-called Super Smash Brothers?"

"Not yet, we will wait for the opportune moment." Thanos said with an evil smirk.

Super Smash Bros x Avengers

Super Smash Bros x Fantastic Four

Super Smash Bros x Amazing Spider-Man

Super Smash Bros x X-Men

Super Smash Bros x Justice League

Super Smash Bros x Star Wars

Super Smash Bros x Mighty Morphin' Power Rangers