DC’s Most Powerful Kryptonite Has Barely Appeared Since It Debuted (& For Good Reason)

Kryptonite is one of the most well-known weaknesses in all of fiction. Superman, being so unbelievably powerful, would naturally need a weakness at some point to keep the story going. Kryptonite, originally appearing as the prototype K-Metal in the unpublished 1940 story “The Secret of The K-Metal,” has become synonymous with a debilitating weakness in pop culture. The classic glowing green rock wormed its way into the everyday vocabulary of the greater populace and became as recognizable as Superman himself. However, green is not the only color Kryptonite can come in, as plenty more variations have been introduced over the years.

There’s Red Kryptonite, which once had random effects, Gold Kryptonite that permanently robs Kryptonians of their powers, and Cobalt Kryptonite that turns Superman giant, just to name a few. However, without a doubt, the most dangerous of all is Black Kryptonite. More so than any other color, this radioactive rock has the power to turn all of Superman’s powers into his greatest weakness, and that is exactly why it seldom appears. In fact, since its reintroduction in Dark Knights: The Batman Who Laughs, it’s only appeared once.

The Deadliest Kryptonite of All

All forms of kryptonite are deadly to Superman, but Black Kryptonite is the most dangerous one because of what it does to the Man of Steel. This rock drags out the worst, most horrific impulses of the person it affects, making their evil thoughts take over and lash out at the world around them. Originally, this kryptonite would split the Kryptonian in two, a good half and an evil half, which was based on the ability it had when it premiered in the TV show Smallville. It first appeared in the season four premiere “Crusade,” where it separated Clark and his Kryptonian personality, Kal-El, into two beings. Of course, the kryptonite became much deadlier in the comics.

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It was used sparingly in the New Earth continuity, once splitting Supergirl into a good and evil half, and once driving Superman to insanity and evil. After the New 52 reboot, Black Kryptonite wasn’t used again until it was reintroduced in Dark Knights: The Batman Who Laughs, where the titular villain used it to force Clark and Jon to skill Lois, and then each other. Even then, this was not in the main universe, but took place in the Dark Multiverse, where everything is based around evil and fear instead of hope. The only time Black Kryponite has appeared in Prime Earth continuity is in Supergirl (2025) #3, where Lesla Lar used it to turn Supergirl and Krypto into villains bent on destruction.

Why Black Kryptonite Is Used So Little

Obviously, transforming characters like Superman and Supergirl into monsters bent on killing everyone around them is not something that should happen all the time. Black Kryptonite is a very dangerous substance, especially for the cohesion of the story. A character as powerful as Superman can bring down entire cities in seconds, so Clark suddenly dedicating himself to doing just that has the capacity to make things far darker than Superman stories are or should be. The Dark Knights issue was meant to be as dark as possible, and Supergirl has a Silver Age, campy tone, so its version of Black Kryptonite only had Supergirl causing property damage and pantsing people. 

Black Kryptonite, by its nature, demands the tone of the story to be held very firmly. It can very easily shift the story into something much darker, and that’s not something that will benefit Superman stories a lot of the time if Superman is the one causing the damage and darkness. Beyond that, there’s the absolute destruction that an evil Kryptonian could unleash, and that alone is more than enough reason to keep this glowing rock under wraps and used only in the most dire of circumstances.

Black Kryptonite has made so few appearances, and I doubt it will be making too many more in the near future. Do you see this as the ultimate Kryptonite, or is there another version that is even more dangerous to the Man of Steel? What do you think? Leave a comment below and join the conversation now in the ComicBook Forum!