Saitama is bored. He trained so hard to become a real hero. Too hard, because now Saitama is just overpowered and every Enemy that crosses his way, is Defeated after Saitama swing a single punch at him.

One Punch Man is a very entertaining and good anime.

Although the anime is a comedy, the fights are really well animated, even if they don't last very long in most cases, because Saitama, as the name of the anime suggests, defeats everyone in one fell swoop.

The relationship between Saitama and Genos is also awesome.

Genos is enthusiastic about Saitama and wants to learn from him, but he really doesn't feel like it at all and rather exploits Genos. From grocery shopping, over cleaning his apartment to fighting monsters he is too lazy to fight. Saitama sends Genos to do it, making him believe it's training.