Piotr Nikolaievitch Rasputin is among the physically strongest of the X-Men. A quiet artist, Peter only reluctantly agrees to fight for the sake of peace. Colossus possesses the power to transform his body into a form of steel, with properties analogous to osmium. While in this state, the mutant requires no food, water, or even oxygen. While Rasputin could withstand great impacts, he is vulnerable to the anti-metal vibranium, which shifts his body to human form. As the unstoppable Avatar of Cyttorak, Colossus has immense superhuman strength, resistance to injury, and other mystical properties, one of which is the ability to ignore impediments to movement, hence the “unstoppable” moniker.
COLOSSUS, by John Gallagher.