How it achieves this is simple; keep it simple. Saitama is a simple guy living in a city who literally just happens to be a superhero. The plot and events in One Punch Man are executed in such a way they don't seem that surprising, they seem natural; They build upon each other and slowly help build plot for what I believe to be a second season, not hat the current season doesn't have a climax. None of the plots or events are boring and none of their conclusions are boring and they all have an effect on the world as whole, which I like since I don't want plot to not have any effect.
In addition the characters are also affected by the unfolding plot. However One Punch Man suffers from what I like to call 'Harem character syndrome' IE. Too many characters. The problem isn't that they introduce too many but that they introduce a plethora of them towards the later half and don't do much with the latter characters as they do with the former ones. Our main protagonist doesn't truly develop but I wasn't expecting him to but they give him a rather good character build in the beginning of the show.
The art work in One Punch Man is Phenomenal. The character all have more or less the same build but are different and noticeable enough that you could easily tell them apart. The fight scenes are where One Punch Man really shines though. Each one feels different and the stakes always seem very apparent because of how much build up each one gets, some getting more than others because of their premise. Where One Punch Man lacks in art is in its stiller scenes between protagonists because the none fight scenes between protagonists and antagonists are entertaining. The varying art styles give the show an odd charm akin to that of 'Panty and Stocking'.
Furthermore the soundtrack accompanying the artwork is great, making each fight scene more epic and enjoyable. The rest of the soundtrack isn't very memorable since it was for scenes that I felt indifferent about. The OP is one of the greatest I've ever heard and is one of my favourite, though the ED feels wasted and more like something I'd hear in a 'feels' slice-of-life anime. The voice acting is good, nothing awe inspiring but I did find it enjoyable.
Lastly I binged One Punch Man in a single day and still enjoyed I emmensly, its not the greatest anime of all time but in my mind its definatley a contender.
In conclusion, what one would expect to find in One Punch Man is great, action packed, epic anime with great art, good music, fantastic pacing and a rather enjoyable piece of mindless fun.
