An interesting plot for a My Hero Academia alternate universe fanfiction could be an AU where there is no UA High School. Instead, there are different academies spread across the world, each with their own unique way of training students with quirks. For example, one academy might focus solely on combat training, while another might be more about quirk research and development. This would lead to different types of heroes emerging from different academies, and there could be rivalries between them. Also, the story could follow a group of students who are trying to bring all the academies together to face a common threat that none of them could handle alone.
Well, in a My Hero Academia alternate universe fanfiction, you could have an AU where quirks are tied to emotions. So when a person is extremely happy, their quirk becomes super powerful, but if they're sad, it weakens. This would add a whole new layer of character development as characters would have to learn to control their emotions to use their quirks effectively. You could also explore an AU where the setting is in a post - apocalyptic world where only those with the strongest quirks have survived, and they are now fighting over the scarce resources left.
How about a fanfiction where the villains and heroes have to team up? There could be a greater threat, like an alien invasion or a powerful quirk - user who is out to destroy the entire world. The heroes and villains realize that they can't defeat this threat alone, so they put aside their differences. This would lead to some really interesting character interactions, like Bakugo having to work with Shigaraki and both of them learning to respect each other's skills despite their opposing natures.
Midoriya is always a great choice. In an alternate universe, say he never met All Might and didn't inherit One For All. He might have to find his own way to be a hero, perhaps by developing a unique quirk - enhancing technology. This would show his determination in a different light. Also, an AU where Midoriya is a villain could be fascinating. We could see how his intelligence and analytical skills would be used for evil, which would be a complete contrast to his usual heroic self.
Maybe a plot where a group of Warhammer heroes are sent to the Hero Academia world to stop a chaos invasion that is starting to seep into that realm. They have to work with the local heroes, sharing their knowledge of dark magic and ancient weapons to combat the new threat. This would involve a lot of cultural clashes and learning experiences between the two groups.
An interesting plot could involve an OC who is initially thought to be quirkless but discovers a latent quirk later on. This OC could then struggle to catch up with the others in terms of training and development. Or, an OC with a shapeshifting quirk could be used in a plot where they have to infiltrate a villain's lair by taking on the form of one of the villains' minions. They would have to be careful not to be discovered and also gather intelligence along the way.
An interesting plot could involve an anti - hero who has a hidden agenda that is not entirely evil but also not in line with the traditional hero goals. Maybe they are trying to expose a corrupt part of the hero society from within. They could form alliances with some villains who also have a vendetta against the corrupt elements. This would create a complex web of relationships and moral dilemmas.
One plot idea could be a villain who is secretly a double agent, working for the heroes all along. They infiltrate the villain group and gather information. Another idea is a hero who loses their quirk and has to rely on their wits and combat skills alone, like Batman in the DC universe. And a villain - hero team - up to face a greater threat that neither can handle alone.
One idea could be an alternate universe where the Fairy Tail guild is a secret organization in a steampunk world. The magic is powered by steam - powered devices and the characters have to adapt their powers to this new technology. For example, Natsu could use his fire magic to fuel steam engines in a more efficient way.
Well, perhaps in this fanfiction's alternate universe, the Mane 6 are all from different species. Rainbow Dash could be a griffin, and they have to overcome the prejudices between their species to form their friendship. It could also be that they are in a post - apocalyptic Equestria, and they are on a quest to find the elements of harmony which have been scattered and lost.
One idea could be a world where the darkspawn and the elves form an alliance. They might come together out of mutual desperation, the darkspawn seeing the elves' connection to the Fade as an advantage, and the elves seeing the darkspawn's numbers as a means to gain power and protection from the other races. Another plot could involve a Dragon Age universe where magic is completely outlawed. Mages would have to go into hiding, and templars would be more like a secret police force, leading to a lot of underground resistance and intrigue. A third idea is an alternate universe where the Qunari have taken over most of Thedas. Their strict way of life would reshape the cultures and societies of the other races in ways that are both fascinating and disturbing.
One interesting plot could be Percy in a steampunk alternate universe. He might have a mechanical sword and face off against steam - powered monsters. Another idea is an alternate universe where the Greek gods are modern - day celebrities, and Percy has to deal with the chaos of their fame while still being a demigod. Maybe in a fantasy - based alternate universe, Percy could be a wizard - like figure, using both water powers and magic spells.