Jax-Ur

Jax-Ur was a Kryptonian scientist who destroyed one of Krypton's inhabited moons during an unauthorized rocket test, killing its population. As punishment, he was sentenced to permanent imprisonment in the Phantom Zone — the first Kryptonian ever condemned to that dimension with no possibility of release.

Few Silver Age villains carry the weight of true infamy quite like Jax-Ur, who burst onto the DC scene in Action Comics #294 in 1962, courtesy of Leo Dorfman and Jim Mooney. A figure dark enough to share pages with Superman, Supergirl, and even Bruce Wayne across a publishing history stretching an remarkable six-plus decades, Jax-Ur has proven far more enduring than a mere footnote. Whether haunting the pages of Superman or Action Comics, this is a character whose presence signals that the stakes are genuinely high — a hallmark of the best the Silver Age had to offer.