Complete Guide To Every X-Men Character Who Returned After Death
30. Colossus
How Did He Die? Injected himself with the cure for the mutant-only disease, the Legacy Virus. The serum that Beast concocted had to be injected into a mutant in order to be disseminated into the atmosphere, at the cost of that mutant's life. Reeling from the death of his little sister Illyana from the same virus (more on her later), he sacrificed his life in order to spread the cure saving countless lives in the process.
How Did He Come Back? Well, it turns out an alien by the name of Ord swapped his body with a double. The double was cremated and Colossus was brought back to life in Ord's lab, becoming a guinea pig for his mutant "cure". Basically, Joss Whedon began writing Astonishing X-Men and wanted to use the character, so... he's back.