I don't know about the original Grunge (I've only been reading the new series) but from what I've seen of the new one and stuff I've read (on databases and such) of the old one, I think he's able to use his powers however he conceptualizes them. Thinking like that, I bet he could get creative and win.
"I would have to go with Iron Man as well. Grunge would need sometihng pretty potent to aborb for Iron Man not to be able to effect him. Plus Iro Man haveing the air advatage helps him a lot."
Wouldn't Grunge just be able to absorb Iron Man's blasts?"
IDK if his reaction time would be fast enough to do it. First few hits I dont think he could, but if he can survive the first bombardment or two then he might get Iron Mans timeing, but Tonys computers are state of the art so IDK.