The original, and best known, is Cain Marko, a long time enemy and some times ally of the X-Men who must be imprisoned in mystic realms to halt his rampaging. After his father married his colleagues’ wife, Cain constantly bullied his step-brother, Charles Xavier, angry that his father favored the gentle, smart Charles to his own son, and was in-turn abused by his alcoholic father regularly. After enlisting in the US army, Marko and Xavier found the Temple of Cyttorak in Korea, where Cain impulsively grabbed a glowing ruby from the lap of an idol and read the inscription “Whosoever touches this gem shall possess the power of the Crimson Bands of Cyttorak. Henceforth, you who read these words shall become forevermore a human juggernaut.” The gem’s mystical power transformed Marko into Cyttorak’s avatar on Earth, the Juggernaut.
He is unstoppable but he was thrown into Magik’s Limbo dimension. It is currently unknown how he escaped.