Is defined One Punch Man a Hero for Fun who is called "Saitama". He can defeat every single foe with a punch. Just one. Not more. Nothing else. Just one fucking punch.
A bald guy named Saitama, who is a hero for fun and he can technically kill people, aliens or whatever he's fighting with - like the car alien- with one punch. He has a "student" named Genos and he's a cyborg, they applied for the hero association and their names are "Bald Cape" and "Demon Cyborg"
It's a very awesome, lit, funny anime so you should watch it.
How to be One Punch Man 101:
"100 push-ups, 100 sit-ups, and 10 km run EVERY DAY
A baldboi who can fucking kill anyone and anything in one punch. He's so powerful in fact, that there's never a single moment when he's at his limit or uses his full power.
A manga/anime series created by ONE about a guy called Saitama, who wants to be a hero for fun/as a hobby. But he become too much powerful, to the point that every opponent ends up defeated with a single punch.