Plot twist, evil Saitama is pitifully weak. He is also called one punch man, but in the sense that anyone including a toddler, can one punch KO him.
*Hero Saitama dashes towards Villain Saitama with a serious punch, realizing that the only one who can finally give him the ultimate challenge he craves is himself and eagerly awaits his greatest fight yet* *Villain Saitama is instantly liquefied upon contact* *Cue Hero Saitama internal screaming*