@the_imperator: So what you're saying is, to kill Doc, you need some sort of supermagical reality-warping weapon. Which means no character can do it without using some magical toys. Doc cannot physucally die (or mentally, as far as we know), so when it comes to Marvel, magic is always the answer, right?
We don't know if the Doc can mentally die or not, though equivalency would suggest that since he never defended against telpathic attacks, he is not going to have any special defense from them. His mind could be subsumed that way.