Cain Marko, better known as Juggernaut, is a powerful mutant and one of the most physically unstoppable beings in the X-Men universe. He is the stepbrother of Charles Xavier and gains his immense strength and near-invulnerability from the mystical Crimson Gem of Cyttorak. As a recurring antagonist and sometimes reluctant ally, Juggernaut often serves as a major brute-force threat to the X-Men, known for his relentless charges, destructive power, and complicated personal ties to the team.