Venom

First host used it to carry out genocide, twisting it into a hate-filled being
Imprisoned on Battleworld by its brethren, they feared it would turn others evil
Found & bounded with Spider-Man, assimilated his powers into its own genome;
Discarded by Spider-Man when he learned it was evil, bounded to Eddie Brock,
Left Eddie, bounded with Mac Gardan turned into a sadistic cannibal;
Removed by the army, given to Flash Thompson, cured from its corruption
Sought redemption, bonded to Dylan Brock, attempted to become a true hero