Noun
kryptonite (uncountable)
(figuratively) The one weakness of something or someone that is otherwise invulnerable, an Achilles heel.
Batman visits her and analyzing her necklace, and discover that it was Red Kryptonite. Source: Internet
But heroes have their kryptonite, and in the cases of Fauci and Birx, that comes in the form of serving at the pleasure of the president—a president who does not tolerate contradiction well. Source: Internet
Computer programmer Gus Gorman ( Richard Pryor ) uses tar to compensate for an unknown component of kryptonite, causing the newly created mineral to eventually turn Superman evil and split the hero into two beings. Source: Internet
A human brain with a cyborg body and a kryptonite heart, he has super strength and agility and can absorb any mechanical or metal object and make it an extension of his exoskeleton. Source: Internet
Exposure to green Kryptonite radiation nullifies Superman's powers and immobilizes him with pain and nausea; prolonged exposure will eventually kill him. Source: Internet
Instead, to protect Superman from sacrificing himself, Captain Atom used it to blow up a giant chunk of Kryptonite that Lex Luthor had steered towards Earth. Source: Internet