I’m kinda going to assume this regen is not only a Saturn thing, though idk if it’s an immortality thing either. Perhaps the branch of mythical fruits the gorosei have, all have crazy regenerative factors. I’m surprised Kuma could massively damage Saturn like this with raw physicality and hardening, because I don’t view Kuma as top tier per se. That being said I’m not going to devalue Saturn as a fighter because of this, what he lacks in durability or endurance, he more than makes up for it in regeneration. Also we don’t know what his haki is like. For Kizaru I still want to believe he’s not the real enemy here, though it would be interesting after everything he’s still trying to kill our heroes, I want to believe he’s pulling a Fujitora here but I can very easily be wrong. All in all really nice developments and a very satisfying Kuma moment.