I won't call it what i want, I'll call it what is wasn't, a nuke. It was a bomb made out of napalm. Also, that's not the same as what Magneto could do to him. There, he was stripped down to a skeleton, a skeleton that protected his brain and allowed him to regenerate. Magneto could crush and liquefy everything, including his brain... he's not regenerating from that. Also, to my knowledge Wolverine has never been decapitated... Magneto could rip his head off quite easily, but he doesn't because Marvel doesn't want their golden boy dead.
As for Deadpool, he can die. Don't confuse not being able to die, with being able to come back from the dead. If i stab you in the face and you die, but then come back to life when the sword is removed, i still killed you.
I dunno what you're trying to say when it concerns Superman and Batman. The reason they don't kill is irrelevant to them being able to kill. Superman can wipe out pretty much everyone, he doesn't do it because the writer's equipped him with a sense of morality. Do you know how many times Superman should have died? Ya know why he didn't die... PIS and the need to continue the story.