Originally posted by MF DELPH
Probably Dr. Strange/Any Sorcerer Supreme, The Doctor (Wildstorm), and/or Dr. Fate since they all have seemingly the same important task in their respective universes (though I think The Doctor's role isn't on a universal scale like the others).
It's not. He's pretty Earth-based in his official "job." The Doctor is often called Earth's Shaman, and long periods of time away from the planet weakens him (though this seems to be largely situational...space doesn't affect him negatively, but being in a different universe for a period of weeks does, for example).
Oh wait, I just figured out who wins this thread:
Jenny Sparks and/or Jenny Quantum. The literal embodiment of a century...the fate of, well, everything in that century is tied to them at an abstract level. It's a little unclear about whether or not this applies just to Earth or the whole universe, but the implication was that it was universal at least with Quantum. Even if it's Earth only, having the fate of the planet tied to your existence is pretty huge, especially since Earth >>>>>>> every other planet in comic universes in terms of overall importance.