Definitely not. Midoriya's character is very much alive in the manga. The creators have no intention of killing him off as he's a key figure in driving the narrative forward and inspiring other characters.
His closest friends like Ochaco Uraraka and Tenya Iida would most likely side with him. They have always been there for Midoriya and share his values of justice and doing what's right. Also, those heroes who have seen Midoriya's growth and believe in his pure intentions would probably join his side.
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.
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.
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.