One possible plot could be that Villain Deku is on a mission to undermine the hero society and crosses paths with Hero Deku. They engage in a fierce battle where Villain Deku taunts Hero Deku about his ideals. In the end, Hero Deku manages to get through to a small part of Villain Deku's conscience, leaving him with some doubts about his villainous path.
In the 'bnha reacts to villain deku fanfiction', different characters would have diverse reactions. Uraraka would likely be heartbroken. She has always seen Deku as a source of inspiration and a good friend. So, seeing him as a villain would shatter that image for her. The teachers, like Aizawa, would be concerned about how the situation came to be. They would probably start to question their own teaching methods and the environment that led Deku to become a villain.
Villain Deku might start to question his villainous ways. Meeting Hero Deku could make him see the good in heroism. Hero Deku, on the other hand, could become more empathetic towards those who turn to villainy. He might realize that there are reasons behind it and not all villains are just 'evil' for the sake of it.
In 'bnha reacts to villain deku fanfiction', the plot might develop as the heroes try to stop Deku from causing more harm. But at the same time, they are conflicted because they know the old Deku. This internal struggle among the characters could lead to some interesting sub - plots. For example, some might try to reach out to Deku secretly to bring him back to the good side, while others might be more aggressive in their approach to stop him.
Toga could be an ally. Since she has her own complex relationship with the idea of heroes and villains, she might find Deku's transformation interesting. She could provide some of her unique skills, like shape - shifting, to help Deku in his villainous plans. Additionally, Twice might also join them because of his loyalty to Toga and his own sense of being an outcast in the hero world.
A possible plot is that Villain Deku has a plan to destroy a major hero institution, and Hero Deku has to stop him. But when they meet, Hero Deku realizes that Villain Deku was once like him, full of hope. This makes Hero Deku hesitant to fight at full force. Or perhaps Villain Deku has kidnapped someone close to Hero Deku, and during the rescue mission, Hero Deku tries to convince Villain Deku to change his ways. Also, they could be from alternate universes where the roles are reversed, and they are forced to interact and learn from each other.
For Hero Deku, his development could be shown by how he reacts to seeing his dark self. He might start to question his own beliefs and actions. For Villain Deku, his development could be in the form of a possible redemption arc. Maybe he starts to see the error of his ways through his interactions with Hero Deku. For example, if Hero Deku shows him kindness or understanding that he never received before.
In a Deku villain fanfic, perhaps Deku could form an alliance with some of the existing villains in the Boku no Hero Academia world. He might see potential in them that the heroes overlook. He could team up with Shigaraki, believing that together they could reshape the world into a more 'fair' place, according to his now - twisted view.
Yes, there are quite a few. You can find them on platforms like Archive of Our Own. Some fanfictions might explore different aspects of a female Deku in the My Hero Academia universe, such as her relationships with other characters, her journey in becoming a hero, or how she copes with the challenges in a different way compared to the male Deku in the original story.