I do not see how Colossus wins "with ease". Iron Monger could casually bust through thick concrete walls/floors, fell several miles and crash landed without any kind of notable damage, and it took a huge arc reactor explosion, after he'd opened up his suit and exposed his body, to eventually put him down. Plus, as pointed out, his actual strength feats at this point are well above Piotr's.
Colossus needs more feats. He has good durability showings at this point, but his strength showings leave much to be desired.