Dante is tough to beat beat but I'm gonna go with Ironman since he has so much prep time.
@ReiKai: Yeah never got the job done on Thor and Hulk sure.
Dante has a shot because of the speed advantage mostly and he can fly as well. But now the OP is changed for two days Dante has this. I don't know how fast Iron Man is really but I know Dante is lightning fast since DMC1 thanks to Alastor and he has Quicksilver. And his father's sword Sparda allows him to unlock his hidden powers thanks to Sparda's blood. His power was so great that he deflected Mundus charged blast with telekinesis. The thing I really hated was despite his great power he was supposedly gonna die from the place collapsing which I thought was pure bullshit lol. Hell I forgot he has Access to his brother's sword Yamato which has tremendous magic power and the ability to cut threw anything. Yep Tony is screw should have followed my first thought.
@MarioRedfield: From what I heard Iron Man is supposed to be a master of prep. Of course not the best like Reed, Pym, or Doom but you know.