Well, from what comics say, as long as one cell in his body survives, he'll get back up. He has survived a nuclear blast (when he was caught in Nitro's explosion during Marvel Civil War.) He's been shot, stabbed, crushed, blown up, dropped out of planes. Not to mention having Magneto rip out his skeleton, (not counting the Ultimate Universe where Magneto's powers let him atomize Wolverine.) And most importantly, covered with scorpions (bonus points to all who get that reference.) The only thing i could think of would be take away his air. I mean, the guy has to breathe.