Real Name: Cain Marko
Mutant Power: Physical nigh-invulnerability; ability to create an impenetrable "force barrier" in front of him when he charges
Voice Actor: Paul Dobson (who also did the voices of Tankorr and Obsidian in Beast Machines, Sideways in Armada, and Rodimus in Energon)
Guest Appearances: "Survival of the Fittest"; "Fun and Games"; "The Stuff of Heroes"; "Self Possessed"
Back Story: Cain Marko, Xavier's half-brother, always had problems with their father, and seemed to be a rather angry individual. He apparently had a big beef with Xavier, as well. Anyway, when Cain used mysticism to make his Mutant powers manifest themselves, he became an incredibly powerful- and dangerous- individual. Xavier regrettably had to lock Cain away before he could cause too much damage. Although Cain escaped once briefly (thanks to Mystique's help), he was kept inside a container filled with paralysis fluid, deep within a maximum security prison. Eventually, though, Mystique busted him out for good, and Cain now has free reign, although he's been "lying dormant" since the X-Men managed to beat him during a fight at a dam.
Personality: Juggernaut's pretty much just mad at everybody, really. Kill Xavier, destroy stuff for fun, smash. That's pretty much his agenda. And the thing is, he can do it, too, as his powers make him nearly unstoppable. Only Xavier's psychic blasts can do any significant damage to him. Due to his immense power, Juggernaut is also not one who allies with anyone else, unless it's a life-or-death situation. So he's pretty much in a team all his own.
Final Reflections: Even though Juggernaut didn't really have much depth to his personality, he was still a pretty cool character, given how it was just practically impossible to hurt him. I wish he would've gotten one more ep after "The Stuff of Heroes", though, since I'd have liked to see what he actually was DOING after the X-Men beat him that one time at the dam.