>>280899915
I'm just realizing... If Oda was introducing regeneration only to introduce anti-regeneration Haki the next arc (and have this guy killed at the end of his own arc), it was a complete waste that he didn't let Kuma's punch severely injure him and arguably take him out.

Haki literally means Will and I don't think we've seen a display of Will as strong as Kuma's in One Piece, especially right after that flashback and having Bonney about to be killed by the guy who experimented and killed his wife.
If any punch had Beyond Haki it was this one. At least show that it slowed his regeneration and he falls again after standing up, then wonders what's up. It's a cool moment but the anime getting there made me realize it could and should have been way stronger.