kryptonite

noun

kryp·​to·​nite ˈkrip-tə-ˌnīt 

variants or Kryptonite

in stories

: a substance that causes the comic-book character Superman to become weak when he is exposed to it

Note: In Superman stories, kryptonite in its most familiar form is a green mineral that originated as part of Superman's home planet of Krypton and that falls to Earth as a meteorite.

Superman tended to get more bummed out by Kryptonite than by anything going on in Clark Kent's life …

—Tom Russo

—often used to describe something likened to kryptonite in causing someone's weakness, failure, etc.

In his career Thome has hit less than .240 against lefties. Lefthanded power pitching is Thome's Kryptonite …

—Joe Posnanski

Ironic people always dissolve when confronted with earnestness, it's their kryptonite.

—Gillian Flynn

"Thin people know they need to either limit exposure to certain foods that trigger appetite or limit the quantity or frequency of those foods," says Gullo, whose personal kryptonite is pizza.

—Lorie Parch

Effortlessly good-looking, he was also a talented writer—that combo was my kryptonite.

—Taylor Orci

Examples of kryptonite in a Sentence

Recent Examples on the Web

Sure, maybe the Steelers have been the exception over recent years, as T.J. Watt and company had often proven to be Jackson’s kryptonite. —Mike Defabo, The Athletic, 22 Dec. 2024

For Superman & Lois fans, did the Superman movie trailer soothe some of the sting of the show’s cancellation/recent end… or simply add kryptonite to the fresh, tender wound? —Vlada Gelman, TVLine, 20 Dec. 2024

For all of his success at the sport’s highest level, Pittsburgh has somehow been Jackson’s kryptonite, pestering him into some of the worst performances of an otherwise Hall of Fame-worthy resume. —Brian Wacker, Baltimore Sun, 14 Nov. 2024

Massive matchup at Roland Garros The only thing standing between Novak Djokovic and his first Olympic gold medal is … Carlos Alcaraz, arguably the Serbian’s biggest kryptonite nowadays. —Torrey Hart, The Athletic, 4 Aug. 2024

Word History

Etymology

Krypton, Superman's home planet + -ite entry 1

First Known Use

1943, in the meaning defined above