Cryptonite

Kryptonite is a fictional material that appears primarily in Superman stories published by DC Comics. In its best-known form, it is a green, crystalline material originating from Superman's home world of Krypton that emits a unique, poisonous radiation that can weaken and even kill Superman and other Kryptonians. Kryptonite radiation can be transmitted through any element except lead. There are other varieties, such as red kryptonite and gold kryptonite, which have different but still generally negative effects.