The Unstoppable Juggernaut is Season 1, Episode 8 of the X-men animated series.
After returning to the X-Men mansion from Genosha, the group notices that the mansion was destroyed. When they land, the group clears the debris. However, there was no sign of the professor in the debris but on reaching the war room, they find a message from Xavier that he departed on a journey. They search for clues about the building collapse, with the obvious being extra large footprints.
Wolverine in search for the attacker finds Colossus, a Russian mutant working to help demolish a building, but discovers that it was not him. However, a short time later, there was a robbery at the local bank, where Colossus was apprehended despite his attempts to stop the attacker. While Wolverine recognizes the same scent at the mansion, Rogue and Storm break Colossus out of the jail. The Russian is at first reluctant to escape, but Beast, who is locked in the cell opposite him, convinces him to trust Rogue and Storm. They also offer Beast a chance to join the jailbreak, but he politely declines.
Meanwhile, at the another bank, Juggernaut rips open the vault door, stealing money. When he is intercepted by Wolverine, he explains he was looking for Xavier. While more powerful than the individual mutants, the group is able to overpower Juggernaut by knocking him down. Jean Grey tries to attack Juggernaut's mind, but she cannot penetrate his helmet, so the X-Men, aided by Colossus, attack the Juggernaut and Rogue rips off his helmet. Rogue then tries absorbing Juggernaut's power, but also absorbs the emotional state complete with the belief of being the most powerful, and the desire to destroy the X-Men.
Juggernaut is finally defeated when Jean gives him a hypnotic suggestion that causes amnesia. However, Jean warns that Juggernaut will at some point regain his memory, she just can't be sure when.
At the end of the episode, the mansion is rebuilt with the help of Colossus. While offered to stay, he declines, since he still needs to find his sister.
Although Gambit was onboard the Blackbird at the end of the previous episode, he is nowhere to be seen in this episode.
Colossus (Pitor Rasputin) and The Juggernaut (Cain Marko) make their first appearances in this episode.