@BlondieBoy How does he put people to sleep? Does he need to touch them or something, or can he just cause sleepyness? Is it resistable? And does it affect beings who do not naturally need sleep.
After doing some more research, I discovered Doomsday (and therefore also Apocalypse) are only able to regenerate at a molecular level. The atomic regeneration is Ultimate Doomsday, which is Doomsday after he spent a few hundred years fighting an infinite army of superman-level opponents. Sorry. That was still in my mind because I originally apped Ultimate Doomsday.
@thewizardguy Hmmm, well the Ethereals discovered that atoms also emitted a form of energy. I suppose we could just say if he's completely atomized he can't be fully revived or something. It makes him a lot less difficult to kill but still horribly resilient.