The one weakness of something or someone that is otherwise invulnerable, an Achilles' heel.(noun)
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Use "kryptonite" in a sentence
"DC owns other elements like Superman’s ability to fly, the term kryptonite, the Lex Luthor and Jimmy Olsen characters, Superman’s powers and expanded origins."
"DC Comics and Warner Brothers will retain rights toother elements like Superman’s ability to fly, the term kryptonite, the Lex Luthor and Jimmy Olsen characters, Superman’s powers and expanded origins."
"(As Larry Elder would say, facts are to liberals what kryptonite is to Superman.)"