One-Punch Man's Saitama is unrivaled, his power absolute. With one punch, he can end the career of a god-tier villain without breaking a sweat. Since his introduction in One and Yusuke Murata's One-Punch Man manga, the biggest question regarding Saitama has always been: what, exactly, is Saitama, and where does his power come from?
Source:https://www.cbr.com/one-punch-man-revealed-secret-saitama-power-monster/