Caliban is one of those tragic characters who started out with a really sad depressing origin and constantly made poor life decisions. What makes him such a compelling character is that you constantly take pity on him.
He originally was introduced as a scrawny, sickly member of the Morlocks–a group of disfigured mutants that crested their own civilization under New York City’s subway system. Instead of being taken into their community with welcome arms, their leader Callisto not only used him in order to take advantage of his mutant tracking abilities but exploited his desire to have a friendship/relationship with X-Man Kitty Pryde.
Caliban eventually found a home with the original incarnation of X-Factor, but even that was short-lived. After the Morlocks were slaughtered by the mercenary Marauders, Caliban sought revenge against them but could not succeed due to his weak nature. To increase his physical capabilities, he wound up making a Faustian deal with Apocalypse that did make him more deadly.
Unfortunately it also left him prone to being under Apocalypse’s control. For the rest of his life he wound up being a member of X-Force until he met his demise twice. This is comics after all.