X-Men #12

Published in July 1965, X-Men #12 marks a pivotal moment in the Silver Age of Marvel Comics, featuring the first appearance of the Juggernaut. The issue was created by the prolific duo of writer Stan Lee and artist Jack Kirby, who sought to expand the X-Men’s rogues' gallery with a character whose immense physical power posed a direct threat to the team. The narrative serves as a bridge between the X-Men's school-based beginnings and the high-stakes, cosmic-scale conflict that would eventually define the franchise.

Jack Kirby’s design for the Juggernaut remains one of his most iconic visual contributions to the Marvel Universe, characterized by the character's massive, domed helmet and armored physique. At the time of release, the book was part of a concerted effort by Marvel to introduce antagonists who could challenge the team on a purely visceral level. The issue was generally well-received by contemporary readers, cementing the Juggernaut's status as a recurring antagonist and a foundational element of X-Men lore.