The success of One-Punch Man is easy to explain, though hard to replicate. It’s a parody that makes fun of western superheroes and typical shonen jump manga series, yet at the same time one-ups the typical action scenes from the shows and comics its parodying. This makes it a show that is a joy to watch even if you aren’t into any of the things its parodying, as it works well on its own.
And the gimmick of the show, which initially sounded extremely limiting to me, the main hero can beat almost any villain with one punch (and by beat I mean transform them into a puddle of blood), forced the series creator to come up with a never-ending stream of unique and interesting villains.
It’s really impressive how the show manages to not feel repetitive at all and makes every new action scene exiting to watch. Some of it comes from the fact that it kind of references other material and then manages to do it even better, but some of it comes from the fact that there’s no filler. The overarching plot moves at a breakneck pace and fires a rapid volley of ideas and jokes at the viewer that almost always hit the mark and don’t give you the chance to get bored.