Kryptonite is a fictional element in DC Comics 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.
- Metallo's Heart is usually made from Green Kyptonite
- Reactron has had a Kryptonite Heart, similar to Metallo, for some time.
- Green Kryptonite has been fashioned into Kryptonite Bullets and Kryptonite Knives.
- The Laughing Dragon was a statue made out of Green Kryptonite.