The first season of One-Punch Man was unlike any other. It turned the typical shōnen series on its head through great fights, hilarious writing, and arguably the most overpowered character in anime. The second season, however, is considered to be a massive let-down. The first season featured the main character, Saitama, in all his glory, while the second focused on less interesting side characters that seemed to slow the anime down. Plus, famed animators Madhouse were replaced by J.C. Staff, which lowered the overall animation quality immensely.

https://screenrant.com/one-punch-man-season-3-save-anime-list/