Well, it could be about the heroes from My Hero Academia getting caught up in the events of Infinity War. Maybe Thanos targets the quirks in the MHA universe. Deku might try to use his One For All to stop Thanos, seeing it as a great evil. And the Avengers could be confused by the existence of quirks at first.
The students of U.A. High would bring a sense of youthful energy and naivete to the interaction. They'd be curious about the powers of the Avengers and their technology. The Avengers, in turn, would be protective of the young heroes at first. For instance, Hulk might initially see the students as too fragile. But as they face challenges together, they'd develop mutual respect. The different personalities, from the cocky Bakugo to the calm and calculating Shoto, would create a rich tapestry of character interactions with the diverse Avengers.
One possible plot could be that the villains in My Hero Academia somehow get their hands on the Infinity Stones. They could use the power of the stones to start warping reality. For example, they might use the Reality Stone to make the heroes' quirks ineffective or change the very nature of the hero society. The heroes would then have to band together, not just from UA but from all over the world, to try and stop the villains from completely taking over. They would need to figure out how to combat the power of the Infinity Stones, perhaps by finding some sort of counter - quirk or ancient hero relic.
One possible plot could be that the Omnitrix from Ben 10 somehow ends up in the My Hero Academia universe. Ben could team up with Izuku Midoriya. Ben, using his various alien forms, could help in hero battles against villains. For example, Heatblast could be useful against ice - based villains in the MHA world. And Izuku could learn a lot from Ben's experience in handling different powers and situations.
The Infinity Gauntlet would likely cause chaos. In My Hero Academia, society is built around the concept of Quirks and how they are used. If the Infinity Gauntlet entered this world, it would introduce a new form of power that is not based on genetics but on an external, extremely powerful object. This would disrupt the existing balance between heroes and villains. Villains might see it as a way to finally achieve their goals of domination, while heroes would have to figure out how to deal with a power that is far beyond what they are used to facing.
One idea could be a crossover with 'One Piece'. The heroes from 'boku no hero academia' could end up on the Grand Line and have to deal with pirates while also using their quirks. Another is a crossover with 'Naruto'. Maybe the students of UA could train with the ninja in Konoha, learning new skills and sharing their quirk knowledge. A third could be a crossover with 'Attack on Titan', where the heroes have to face the Titans and figure out how to use their quirks to defeat these huge threats.
Maybe the plot involves a device created by Stark Industries that malfunctions and creates a portal between the two universes. The heroes from both sides initially have some misunderstandings and fight each other. But then they realize that there is a greater threat. The My Hero Academia students could learn a lot from the Avengers' teamwork and fighting styles, while the Avengers are impressed by the creativity of the quirks. They then join forces to stop a group of villains who are trying to use the portal to invade both worlds.
Well, it could be that Spider - Man gets transported to the My Hero Academia universe. Maybe he teams up with Midoriya. They could learn from each other's powers. Spider - Man could show Midoriya some new ways to use his One For All power, like how to be more acrobatic during battles. And Midoriya could teach Spider - Man about the quirks system in their world.
One idea could be that the Pokemon have Quirks. For example, Pikachu could have an electric - based Quirk that is even more powerful than its normal electric attacks. The heroes in training from My Hero Academia could team up with these special Pokemon to fight against villains who are also using Pokemon with dangerous Quirks. It would be a really cool mix of the two universes.
One great 'My Hero Academia' crossover fanfiction is the one where they cross over with 'One Piece'. It combines the unique powers of the 'My Hero Academia' world with the adventurous and diverse world of 'One Piece'. The characters interact in really interesting ways, like Midoriya being amazed by Luffy's Devil Fruit powers and Luffy being intrigued by the concept of Quirks.
One idea could be that Kakashi is somehow transported to the My Hero Academia world. He could become a teacher at UA, using his ninja skills and wisdom to train the students in new and unique ways. His Sharingan would be a very interesting power in the MHA universe.