One-Punch Man's titular character being overpowered is no secret to the anime community. He is so powerful that fans often compare him to strong characters from other franchises. Most even claim he can complete his signature one-hit knockout with them. After all, Saitama defeats most of his opponents with a single punch, so it makes sense that a cross-universe match up would be no different.
Source:https://www.cbr.com/saitama-strongest-attack-one-punch-man/