I think Magneto would take this one. He's really powerful, an omega level mutant if I'm not mistaken. He controls electromagnetism which is one of the four fundamental forces of the universe and he could probably destroy the Earth if he wanted to.
"Magneto can maintain total control of an entire planet's electromagnetic field and manipulate it accordingly. Magneto has harnessed magnetism to stop armies, raise islands from ocean floors, move mountains, change the course of rivers, and threaten to devastate the world with apocalyptic floods and continent shaking earthquakes. Magneto once blanketed the entire globe with a self-generated electromagnetic pulse that caused widespread devastation." From marvel wiki
He's also able to create magnetic forcefields which can withstand nuclear blasts.
I don't know who Myotismon can digivolve to other than Venom Myotismon and Malo Myotismon but I'm pretty sure neither is powerful enough to stop Magneto.