Summary

• Kryptonite only works on a Superman from the same universe, as revealed in Infinite Crisis.
• During Infinite Crisis, an alternate Superman from another universe is unaffected by kryptonite.
• Superman can avoid kryptonite by traveling to another universe, eliminating his greatest weakness.

Superman's greatest weakness has always been kryptonite. While in the presence of kryptonite, Superman loses all of his abilities, and the radiation will eventually kill him. During one of DC's major crises, a shocking detail about kryptonite was revealed: kryptonite only works on a Superman from the same universe as the iconic green rock.

During a particularly tense conversation in Infinite Crisis #3 by Geoff Johns, Phil Jimenez, George Pérez, Andy Lanning, Norm Rapmund, Wayne Faucher, Guy Major, Jeromy Cox, and Nick J. Napolitano, Batman comes face to face with a version of Superman from another universe. This Superman is trying to convince Batman to let his reality be overwritten.

Naturally, Batman is unconvinced and brings out his classic kryptonite ring to take down the alternate Superman. Shockingly, this kryptonite has no effect at all. The older Superman is completely unaffected by the kryptonite and even uses his heat vision to immediately destroy it. The older Superman explains that unless the kryptonite comes from the same Krypton as the Superman in question, it will have no effect.

Infinite Crisis #3 also includes the first appearance of Jaime Reyes, who becomes Blue Beetle shortly thereafter.

Kryptonite Is Superman's Biggest Weakness, But Only In His Universe

Art from Superman #8 by Joshua Williamson, Jamal Campbell, David Baldeón, Gleb Melnikov, Rapmund, Alejandro Sánchez, and Dave Sharpe

When the planet Krypton was destroyed, the explosion irradiated tons of debris and then launched it through space in every direction. This radiation has a lethal effect on any Kryptonian who comes into with it. They will grow increasingly sickly, lose all of their powers, and eventually die if they continue to be exposed to the kryptonite. These effects are a simple "Superman rule" that almost every fan — and villain — of the DC Universe knows. But this encounter between Batman and the other Superman shows an incredible detail that most overlook: kryptonite can only hurt a Superman from the same universe as that kryptonite.

Readers have seen a few alternate versions of Kryptonians over the years, and they've all obeyed this unexpected rule to some degree. Ultraman — an evil version of Superman from another universe — not only isn't affected by Kryptonite but snorts it up for a power increase. Unlike Supergirl — who is as weak to kryptonite as her cousin — Power Girl is also a Kryptonian from another universe, and while Power Girl has some strange eaknesses, kryptonite doesn't seem to be one of them, with her easily shrugging it off in the past.

Superman Won't Have to Worry About Kryptonite If He Goes to Another Universe

Superman's Greatest Weakness Doesn't Matter in the Multiverse

Superman is an absurdly powerful character, and he has few weaknesses that villains can exploit. Now, thanks to a few different sources and clues, it seems that Superman could just negate his biggest weakness entirely by going to another universe. With how many adventures the Justice League goes on, a multiversal trip isn't out of the ordinary for them. Now Superman will never have to worry about kryptonite — so long as the kryptonite isn't from the same universe as him.

Infinite Crisis #3 is available now from DC Comics!