The X-Men #18

Magneto dominates the cover of this 1966 Marvel issue, red-caped and triumphant with fist raised, as a stricken Iceman falls helplessly before him in a blaze of light — the title "If Iceman Should Fail--!" making the stakes unmistakably clear. The faces of the other X-Men — Cyclops, Marvel Girl, Beast, and Angel — look on from the sidelines, with Angel also visible in action above, lending the composition a real sense of mounting tension. With cover art by Jack Kirby, Werner Roth, and Sol Brodsky, and interiors from Stan Lee, Jay Gavin, and Dick Ayers, this is silver-age Marvel mutant storytelling firing on all cylinders.