2006’s X-Men: The Last Stand might have introduced Juggernaut to the silver screen (Vinnie Jones) but it was 2018’s Deadpool that introduced moviegoers to a more canon version of the character. The latter is portrayed by David M. Leitch, an American filmmaker, stunt performer, stunt coordinator, and actor, although the character was actually voiced by Ryan Reynolds himself. Comic book fans of X-Men have actually known Juggernaut for quite some time now, since the character first appeared in 1965’s The X-Men #12 as the human step-brother of Professor X, whose sibling is set to appear in Deadpool & Wolverine.
Juggernaut, one of X-Men’s most formidable adversaries, harbors a deep-seated animosity towards his step-brother Charles Xavier, stemming from childhood resentments and a series of life-altering events. Despite moments of redemption and heroism, his bitter hatred towards Xavier and the X-Men persisted, fueled by his perceived injustices and personal struggles. The complex dynamic between Cain and Xavier has shaped their tumultuous relationship, with the Juggernaut remaining a formidable antagonist in the ongoing saga of the X-Men.
Many of Juggernaut’s reasons to hate Charles were actually tied to their shared childhood and adolescence. Juggernaut’s real name was Cain Marko, and unlike his step-brother Charles Xavier, he was born completely human, without any X-Genes. After Cain’s mother died, his father married Sharon Xavier for her great wealth (her husband, Dr. Brian Xavier, also died). This brought Cain into contact with Charles Xavier, whom Cain’s father, Kurt Marko, favored over his own son.
This led to Cain often bullying young Charles, being abusive to him at every opportunity he got. In return, however, Dr. Marko would often beat Cain. At that time, Charles’s telepathic powers began to emerge, and he started experiencing Cain’s anguished thoughts and emotions after the latter had been beaten by his father. Since Charles wasn’t in full control of his power just yet, Cain eventually sensed that Charles was capable of reading his mind and that he had discovered Cain’s secret shame.
Soon after, Sharon died. Following an altercation between Cain and his father, their mansion caught fire. Dr. Marko managed to save both Cain and Charles but died of smoke inhalation. In his last moments, he tells Charles to keep his powers secret from Cain, but Cain overhears them, which leads him to believe that Charles has been deliberately invading his thoughts. From that moment on, Cain regarded Charles as his enemy.
The mansion was repaired, and the brothers continued living together, with Cain becoming increasingly resentful of Charles’s athletic and academic achievements and his telepathic powers as time went by. At one point, as young adults, Cain pushes Charles too far, and the two get into a fight, which Charles wins. This drives Cain to leave their home and go into the unknown. What happened in the intervening years is largely unknown, but at some point, Cain fell into the role of a mercenary, and years later, he and Charles found themselves serving together in the same unit in the Korean War.
Cain deserted under fire, and Xavier ran after him to bring him back, following him into a cave that actually housed the lost secret Temple of Cyttorak, an immensely powerful extra-dimensional being hailing from the Crimson Cosmos, who has been worshiped as both a god and a demon by primitive humans. Inside the cave, Cain grabbed a glowing ruby from the lap of an idol, which instantly turned him into a large, superhuman being: a human juggernaut. At that moment, the cave collapsed due to bombardment, and while Charles managed to escape, Cain was trapped under the rubble.
Due to the fact that he’s now the avatar of Cyttorak, Cain didn’t need air or food to survive, and with his newfound strength and invulnerability, he managed to dig himself free. He soon relinquished his soul to Cyttorak, which completed his transformation into the Juggernaut and solidified his resolve to use his newfound strength for revenge against those he believed had wronged him, especially Charles.
Along with his powers, Juggernaut was also granted a full suit of mystical armor by Cyttorak, forged from the metal found in the Crimson Cosmos. This includes the now-iconic helmet, which is particularly important, as it shields him from psychic attacks. This conveniently proves a necessary defense against Charles Xavier’s telepathy. He returned to America and tried to kill Charles on several occasions; in one of those, the X-Men managed to remove his helmet so that Charles could psionically subdue Juggernaut.
As a response, Juggernaut went back to the Crimson Cosmos and acquired a skull cap as a form of additional protection in case his helmet got knocked off again. So, while it’s easy to understand that Juggernaut’s hatred of his brother stems from childhood trauma, Juggernaut has demonstrated unusual compassion toward mutants despite not being one. He even teamed up with the X-Men on certain occasions, one of which led to him losing his powers.
Upon searching for refuge and a new start in the mutant nation of Krakoa, however, his entry was barred by none other than Charles, who said that Juggernaut isn’t a mutant and, hence, can’t be granted entry to Krakoa. Here’s the thing: that is a lie. It was confirmed that family members of the mutants are also granted entry despite not having the X-Gene. So, while Juggernaut is often painted as an antagonist and a villain, at least he’s honest in his hatred towards Charles. Charles, on the other hand, resorted to lies to deny his brother shelter when the latter was at his most vulnerable.