My Hero Academia
The world's greatest Hero, All Might's real Quirk is not known to the public and most people say that he has some strength-enhancing Quirk. He passes his quirk on to Izuku after seeing the boy's bravery. He is a teacher at U.A. High School, doing his best to allow Izuku follow in his foot steps. His One For All Quirk allows him to pass on his powers to another, which he plans on doing, as five years before, a fight with a Villain left All Might terribly injured to where he can only use his Quirk for three hours a day. This time limit later goes down slowly after passing his Quirk to Izuku, until it finishes completely. The nature of his Quirk is only known by Izuku, the school principal, Recovery Girl, and a few other Pro Heroes (with Katsuki later finding it out), and must not be revealed at any cost in order not to destroy people's symbol of peace. After defeating his archenemy "All For One", the same Villain who injured him, in a final battle, All Might retires from being a hero, focusing on being a teacher and to raise Izuku as his successor.