Sure, Deku takes on the role of a vigilante in the manga. It's a bold move that showcases his growth and the challenges he faces outside the conventional system of heroes.
One great Izuku quirkless fanfiction is 'A Different Path'. It shows Izuku finding his own way to be a hero without a quirk through sheer determination and intelligence. He uses his knowledge of hero strategies and martial arts to hold his own against quirk - users.
One of the best vigilante novels is 'The Dark Knight Returns' by Frank Miller. It presents a gritty and aged Batman coming out of retirement to clean up Gotham again. Another great one is 'V for Vendetta' by Alan Moore. The story of 'V' fighting against a totalitarian regime is both thrilling and thought - provoking. Also, 'Watchmen' by Alan Moore is considered a classic in this genre, with complex characters and a deep exploration of the concept of vigilantism.
The Punisher is also a great example. Frank Castle, after his family is brutally murdered, takes the law into his own hands. He hunts down criminals with extreme prejudice, his no - nonsense approach making for a gritty and intense vigilante story. He doesn't abide by the normal rules of law enforcement, but he has his own code of justice.
Start by creating a strong and relatable protagonist. Give them a clear motivation for taking justice into their own hands. Also, build a complex villain or system they're up against.
Start with a compelling hero. Make them have a strong sense of justice and a reason to take matters into their own hands. Also, build a complex villain to create tension.
One interesting quirkless oc fanfiction could be about an ordinary person in a world of quirks who uses their wits and determination to outsmart villains. For example, they might study the weaknesses of quirk - using opponents and use strategic planning to achieve victory.