Piotr Rasputin, also known as Colossus, (performed by Daniel Cudmore) is a Russian mutant.
- Organic Steel Transformation: Colossus is a mutant with the superhuman ability to convert the tissue of his entire body into an organic steel-like substance. This substance resembling steel is of unknown composition but appears to be analogous to osmium and to carbon steel. He is able to transform into this armor-like state at will (the process is virtually instantaneous) and remain in that form for an as yet undetermined amount of time. (The longest time he has remained in armored form by choice so far has been five days). Once in his armored form he remains so until he consciously wills himself back to normal. If he is rendered unconscious, however, he spontaneously reverts to his normal form. While in the armored state, Colossus possesses the same degree of mobility that he does in his normal form. The conversion from flesh and bone to organic steel is accomplished by a psionic whole-brain interface with an ionic form of osmium, an extremely dense metal, located in another dimension. In willing the act of transformation, Colossus actually exchanges osmium atoms for his carbon atoms. The psionic interface with the other dimension re-creates all of Colossus's body in functionally similar organic ionic-osmium materials. The process by which Colossus gains additional mass from an unknown, perhaps extra-dimensional, force remains unknown. Colossus cannot become partially or selectively armored; his body is either entirely converted or not.
- Superhuman Strength: After transforming into his armored state, Colossus possesses vast superhuman strength. As a teenager, he was sufficiently strong enough to lift about 70 tons. However, as a fully mature adult, his strength has increased, though the exact amount he can lift isn't clear. It is known that he is able to lift at least 100 tons .
- Superhuman Stamina: Also, while in armored form, Colossus' musculature produces considerably less fatigue toxins than the musculature of a normal human. At his peak, he can physically exert himself at peak capacity for several days before the build up of fatigue toxins in his blood begins to impair him.
- Superhuman Durability: In his armored form Colossus is invulnerable to most forms of bodily harm. His armor is capable of withstanding ballistic penetration, including that of a 110 millimeter Howitzer shell. He can survive extremes of temperature from 70 degrees above absolute zero (-390 degrees Fahrenheit) to over 9000 degrees Fahrenheit. He could survive a collision with a loaded, one-ton flatbed truck at 100 miles per hour or an explosion of 450 pounds of TNT. Colossus' body attracts electricity like normal metal but he is actually immune to the effects of it himself. He can also survive falls from great heights while in his armored body. Colossus tends to jump at foes from a height creating a shock wave when he lands, due to his armored form. He can go without food, water, or air for many days while transformed, though he would eventually require sustenance.