Short version, One Punch Man is Japan’s version of The Tick mocking the Superhero conventions they have.
Long version, Punch is like The Tick but it mocks all the Japanese anime tropes featuring cyborgs, monsters (or kaiju), ninjas, superhero organizations (in Punch it acts more along a sports league with them being rated). The hero Saitama isn’t delusional, he’s more blasé and annoyed because his superpower makes any encounter unchallenging; as per the title, Saitama always defeats someone with one blow. On the side he’s also trying move up in the rankings while juggling day-to-day life; in a recent adventure, he rushes to fight a monster before a nearby sale is over.
I would recommend this to those who love superhero shows and/or others not that into anime. Trust me, I’m pretty selective too and am often confused by all the different Gundam shows, where the hell is Big O going and I would rather see Space Battleship Yamato.
The first season is now Netflix.