If you've never really been into anime, then stop reading because this show isn't for you. If you've occasionally dabbled, then watch. I had been told to watch it for some time and finally gave in.
The title speaks for itself. The show is about a hero who defeats everything in one punch. I was so reluctant to watch it initially because I wasn't sure where the conflict would be. He really does kill everything in one punch. However, it's the internal struggle that drives the story, the wrestle with discontentment and boredom when given complete power, the search for meaning even after you've perfectly accomplished your life's goal.
Or it's just making fun of other anime. Anyway, the show is hilarious. You'll have a good time.