Responses
Nurarihyon No Mago is a little like that (MC has two forms- night and day. Night one is badass and strong but as soon as he reverts back he forgets what he's done)
http://www.mangago.zone/read-manga/tal/
http://www.mangago.zone/read-manga/black_clover/
http://www.mangago.zone/read-manga/isekai_de_kuro_no_iyashi_te_tte_yobarete_imasu/
http://www.mangago.zone/read-manga/the_reincarnated_one_doesnt_want_to_cheat/
http://www.mangago.zone/read-manga/switch/
http://www.mangago.zone/read-manga/bungou_stray_dogs/
Heya does anyone know of any shounen /superpower manga when the main character is like really strong but he doesn't realize it cause he kinda blacks out if u get what I mean Thanks xx