The Vigilante's Rehab

Izuku will be a vigilante in the beginning but will eventually be put on a rehabilitation programme. Izuku will still be quirkless but will be training since the age of 5 but will hide all of his muscles using baggy clothes so he won't be suspected. Izuku will have 'Adoptive Muscle Memory'. (The power to replicate movements after observation.) This is how Izuku was able to master a lot of martial arts in such a short amount of time. Izuku will just watch fights on certain martial arts as well as heroes to replicate and master their moves whilst minimalizing the amount of errors. Izuku will be using a lot of weapons and anyone who has encountered him has described him as a demon. This is mainly because he has the strength capable of killing a bear and the speed that puts a cheetah to shame. Include this in small areas where he can use the walls to increase speed and you got your self a deadly weapon capable to outmatch even the likes of All Might to shame. He got this strategy after watching Gran Torino use it and he was only able to watch him fight by hacking into cameras which he learned from watching it happen. (Okay, so Izuku's ability 'Adoptive Muscle Memory' also allows him to copy any action performed by others as long as he has seen it once even if it's on TV, this is really useful but isn't a quirk and it's just apart of his brain much like a photographic memory.)