One Punch Man 2

The second season of One Punch Man.

Saitama is a hero who only became a hero for fun. After three years of “special training,” he’s become so strong that he’s practically invincible. In fact, he’s too strong—even his mightiest opponents are taken out with a single punch. Now, the great seer Madame Shibabawa’s prediction about the Earth being doomed seems to be coming true as the frequency of monster incidents escalates. Alongside Genos, his faithful disciple, Saitama begins his official hero duties as a member of the Hero Association, while Garou, a man utterly fascinated by monsters, makes his appearance.

(Source: Anilist)

He was the best disciple of Bang's dojo, until he went on a rampage against the other students and disabled many of them for life. He was expelled after getting a beating by Bang.  He eventually becomes the strongest villian, ranked as a Dragon + level threat (considered around the same strength as Boros). Using his 'God-Slayer Fist', he easily defeats Golden Sperm and most of the remaining S-Class heroes. In an epic fight with Saitama, the man is ultimately defeated but manages to escape before the heroes are able to get rid of him for good.

One Punch Man 2 Characters