Don't really know.OPM has the problem of having either extremely overpowered characters or simply strong buff dudes.Saitama and Boros are very OP and not even the likes of Madara would be able to top that.The rest is made up by very physical users who use punches or swords, but don't have elemental powers like ninjas or strange stuff like devil fruit users. Itachi would obliterate everyone of the S class. The only one who stands a chance is Tatsumaki because she's a psychic, but that's also unfair...