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