Will Ronda Rousey hypothetically defeat X-Men's Colossus in a fight? Think carefully first, then make a decision:
Ronda Rousey is a mixed martial artist and wrestler. Ronda Rousey relies on striking moves and submission tactics to dominate her opponents. X-Men's Colossus has the ability to change his appearance. Colossus's mutation allows him to create an organic steel layer, that acts as an impenetrable external shell. So, the answer is no.