Board Thread:Versus Battles/@comment-27861278-20181013215759/@comment-31165326-20181015231108

His serious punch deflected a High 6-A attack. Planet level was long since debunked by translations.

Saitama however has been stated to be able to blow up the planet, which is presumably a bit closer to his max. Saitama doesn't null Regen, he overpowers Regen via sheer... Power. And considering Izzy isn't High 6-A, Saitama wouldn't be able to pull the same trick. Besides, he only really brute forced' Garou, Boros just used up all his life energy and had his gemstone that was in the ship crash.

Saitama would take Izzy just as seriously as vice versa.