For a marvel's avengers game fanfiction plot, you could focus on the relationships within the team. For instance, what if there was a rift between Iron Man and Captain America again, but this time it was caused by a misunderstanding about a new technology that could potentially save or destroy the world. Or perhaps a story where Thor brings a new Asgardian to Earth to train with the Avengers, but this new character has a dark secret that endangers the team. Additionally, a plot where the Hulk goes on a solo adventure and discovers a hidden part of himself that changes his relationship with the rest of the Avengers would be an engaging read.
One idea could be Captain Marvel bringing back some alien tech that the Avengers have to figure out how to use. It could lead to new powers for some of the members or a new way to defend Earth.
A great concept for Marvel Avengers crossover fanfiction is to have the Avengers cross paths with the Fantastic Four. The two teams could collaborate on a scientific project that goes awry, creating a new threat that only their combined powers can defeat. Another possibility is a crossover with the Eternals. Since the Eternals have been on Earth for a long time but hidden, their discovery by the Avengers could lead to a complex relationship. They might initially be at odds, but then realize they need to work together to stop a greater evil that is awakening on Earth. Also, an Avengers crossover with Blade would be interesting. Blade could seek the Avengers' help in fighting a new breed of vampires that are more powerful than ever and have ties to some dark magic that the Avengers have to figure out.
A plot could be about an alternate universe where Captain Marvel is initially distrusted by the Avengers. She has to prove herself and in the process, they all learn more about each other's powers and pasts. This could lead to some great character development and new alliances within the team.
Imagine a fanfiction where Captain Marvel uses her energy - based powers in a completely new way during the final battle in Avengers: Endgame. Instead of just punching and flying around, she could manipulate the energy fields in a way that disrupts Thanos's entire army. This would be a creative take on her character and her abilities.
A really cool plot idea could be that the Avengers are watching Endgame in a sort of 'alternate reality cinema' where the events in the movie start to bleed into their real world. So they have to stop the movie from fully playing out to prevent chaos in their own universe. This would involve a lot of action and strategic thinking as they try to stop things like Thanos from emerging from the screen while also trying to understand the significance of what they're seeing in the movie.
One possible plot could be that the Avengers are facing an extremely powerful new enemy that they can't seem to defeat. Captain Marvel arrives on Earth just in time. At first, there are some misunderstandings and clashes of egos among the Avengers and Captain Marvel. But as they start to work together, they realize each other's strengths. Captain Marvel's raw power combined with the Avengers' teamwork strategies slowly turn the tide of the battle. Eventually, they defeat the enemy and Captain Marvel decides to stay on Earth for a while to help the Avengers train for future threats.
Perhaps the Avengers mistake one of the Horsemen for a new super - villain. As they engage in battle, they soon realize that the Horsemen is actually after a powerful artifact that a real villain in the Avengers' world has obtained. So they form an uneasy alliance to retrieve the artifact.
Maybe in the fanfiction, the multiverse is collapsing and the Avengers of different universes are brought together by a mysterious force. They find out that an experiment gone wrong in one of the universes has caused this. So they have to travel through different universes, each with its own unique versions of the Avengers and villains. Along the way, they discover new powers and abilities that they can use to try and reverse the damage and save the multiverse.
One interesting plot could be the Avengers facing a new, super - powerful villain made of an unbreakable steel - like substance. They have to figure out how to defeat it without their usual methods working.
One interesting plot could be the Avengers facing an ancient, all - powerful cosmic entity that threatens to destroy all of existence. They have to combine their powers in ways they never thought possible, like Iron Man's technology with Thor's magic.