Kryptonite is a fictional element in the DC Comics universe, and one of the few items that can harm Superman, his cousin, Supergirl, and his dog, Krypto.
It is able to kill the Man of Steel should he stay in contact for a long period of time. Some of its notable users are Lex Luthor and Metalllo.
Kryptonite comes in many different forms, though the most infamous is Green Kryptonite. Each Kryptonite variant has vastly different properties but are in general harmful to Kryptonians.
However, Kryptonite is unique to each universe, meaning Kryptonite from Earth-1 will not work on Earth-3, Superman, or vice-versa. This came into especially great effect with Superboy-Prime, whose universe lacked Kryptonite, and thus made him one of the few Kryptonians in existence with a complete immunity to Kryptonite.
Green Kryptonite is the most common and iconic state of Kryptonite. It causes great discomfort and weakness in Kryptonians, as well as radiation poisoning in other life-forms. For example, Lex Luthor contracted cancer from prolonged exposure to Green Kryptonite.
Gold Kryptonite has the ability to instantly depower Kryptonians. Unlike Green Kryptonite, prolonged exposure to Gold Kryptonite will permanently depower Kryptonians, and deny them the ability to gain superhuman powers. In effect, this turns them into ordinary humans.
Red Kryptonite changes Kryptonians personality into evil which makes him lose all inhibitions and becomes unpredictable of his actions.
Black Kryptonite causes Kryptonians to split into two different entities, one embodying the "evil" side of the personality.
- Metallo's Heart is usually made from Green Kyptonite
- Reactron has had a Kryptonite Heart, similar to Metallo, for some time, however his is usually of the more dangerous Gold Kryptonite.
- Green Kryptonite has been fashioned into Kryptonite Bullets and Kryptonite Knives.
- The Laughing Dragon was a statue made out of Green Kryptonite.
- Injustice Batman utilized a Gold Kryptonite Dagger to try and stop Injustice Superman.
- Firestorm is shown to be capable of creating Kryptonite via molecular manipulation.
- In most Superman or Supergirl boss encounters in DC Online, the player-villain will use Green Kryptonite to weaken the heroes, and allow them to be fought.
- Almost all Superman villains (Lex Luthor, Kryptonite Man, Kryptonite Woman, etc.) have this as their motive, which is due to it being one of the few things capable of harming Superman.