Definitely All Might. His incredible strength and experience would make him a formidable opponent against the Kree. He could inspire the other heroes to fight back and not be intimidated by the alien invaders.
Shoto Todoroki could be a key defender as well. His ability to control ice and fire gives him a wide range of offensive and defensive capabilities. He could use his ice to immobilize Kree soldiers or his fire to counter their energy - based attacks.
Perhaps a powerful villain in the My Hero Academia universe made a deal with the Kree. The villain could offer the heroes of that world as subjects for the Kree's experiments in exchange for power or technology. This would lead to the Kree invasion as they come to collect their 'prizes'.
Well, if a character was half Kree and half human in My Hero Academia fanfiction, their abilities could be a really cool mix. The Kree are known for their advanced technology and physical strength in the Marvel universe. So this character might have enhanced strength like a hero in My Hero Academia who has a strength - based quirk, but it could be on a different level. Maybe they could also have some kind of energy - based power from the Kree side that they could use in combat, like shooting out blasts of energy while also having the ability to use their human - like intelligence to strategize in battles.
His quirk could be something like 'Limitless Rage - Transformation'. When he gets angry, his body transforms into the Hulk form, growing in size and strength. The angrier he gets, the more powerful he becomes, similar to how it works in the Hulk's original story.
Batman in the My Hero Academia world would likely be a bit of an outsider at first. His dark and brooding nature might contrast with the more colorful and often optimistic characters in MHA. However, his intelligence would be highly respected. He could use his detective skills to help solve some of the mysteries that pop up in the MHA world, like the origin of certain quirks or the identity of villains who are hiding in plain sight. And his martial arts expertise would make him a formidable opponent in battles against villains.
In such a fanfiction, from Naruto, Sakura could be in the harem. She's strong - willed and has her own set of skills. From My Hero Academia, Ochaco Uraraka could be there. She's kind - hearted and has an interesting quirk. And of course, Hinata from Naruto is also a likely candidate with her shy yet determined personality.
A possible backstory could be that the Kree half of the character was part of a Kree experiment to study other planets, including Earth. During this experiment, the Kree individual fell in love with a human. Their child, the half - Kree half - human, was then born. This character could grow up with a sense of being different, always having to hide their true nature. They might have seen their Kree parent being hunted by other Kree who didn't approve of the inter - species relationship. As they grow older, they decide to use their unique abilities in My Hero Academia's hero - filled world to prove that being different can be a strength and to protect those who are also outcasts.
In a 'Ben 10 My Hero Academia Crossover Fanfiction', Ben Tennyson would be a main character. He has the Omnitrix which is full of possibilities. Another main character could be Ochaco Uraraka. Her gravity - controlling Quirk would be an interesting contrast to Ben's alien powers. They could work together in some really cool ways, like Uraraka using her Quirk to levitate Ben in a strategic way during a battle. And then there's also Tenya Iida. His speed and strict sense of justice would add another dynamic to the group. These characters would all play important roles in the story, whether it's in combat, strategizing, or just in their interactions with each other.
In a fanfiction setting, Bakugo might be the most powerful. His explosive quirk is already very destructive. At Hogwarts, he could learn some offensive magic spells and combine them with his quirk for some really powerful attacks. He's also highly competitive and would strive to be the best, which would drive him to master both his quirk and magic faster than others.
All Might could also be an interesting choice. If someone was reincarnated as a younger All Might, they could change some of the events that led to his decline in health. They could also learn from his mistakes and become an even more powerful and long - lasting symbol of peace.
I think Deku would be really interesting. He could be sharing his thoughts on how he's constantly trying to improve his quirk and live up to All Might's legacy. His nervous but determined personality would add a lot of charm to the sleepover.