This is a very creative new anime. You will enjoy this anime if you have an affection for action packed theatricals. I was going to give a 10 but there is one problem. The characters have no backstory!
Story: 10
The story is about an over powered protagonist trying to make himself known to the world. He encounters having an apprentice and fighting lots of battles mostly ending in one-punch.
Art: 10
The art style is very well drawn with no noticeable errors.
Sound: 10
Excellent and this particular anime has a great sounding theme and opening songs.
Character: 8
The protagonists are told to have very dark past and in particular the apprentice. But after one whole season we do not have any information on One-punches past at all. (I'm sure done intentionally.) All we are told is he was able to gain enormous psychical strength over 3 years. Also the main antagonists are not directly identified until being "suggested" in the last episode.
Enjoyment: 10
Personally I love action packed anime. Despite many similarities to DBZ, I found that this anime did not draw out needless storytelling.
Overall: 9
As I previously stated I could not give this anime 10 due to the lack of character development. I understand that the background of the characters will be revealed in the next season. But in every single T.V series I have watched where the single most important backstory is held back for so long always ends in disappointment. (LOST for example) I do not expect the next season to be better but far worse.