Didn’t realise they had started an Anime of it. I’m an avid follower of the Manga. 
Onepunch man is just a brilliant premise (the main character is so ridiculously powerful that he beats all his opponents with one punch), and whilst it seems like they’d run out of ideas pretty quickly with an unbeatable hero, they’ve kept it going brilliantly so far.
Great humour in it as well, not least because the hero is completely bald. Can definitely recommend as easy, fun reading that’ll give you a good chuckle. 
http://img.bato.to/comics/2012/11/09/o/read509d12c997d18/img000009.jpg