ReadingDangerously
I mean... even if Riser can heal from POD getting his chest disintegrated slowly by an orb while healing would be extremely painful to the point he'd probably give up long before either would run out of power. Heck, their whole thing is 'oh no he can heal fast' just stab him in the spine and keep the blade inside his body. Can't really heal while it's still inside them. It's one of those very obvious solutions to regenerators that aren't really explored because watching the weapon slowly fall out makes for very cinematic scenes.