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n. Slang
Something that presents a particular threat to one that is otherwise powerful: Immigration reform turned out to be the senator's kryptonite.

[After Kryptonite, a fictional radioactive mineral (the presence of which weakens the superhero Superman) appearing in Superman comics from 1949 onwards : Krypton, the home planet of Superman where Kryptonite was once found before being scattered in the universe by the planet's destruction (named by American comics writer Jerry Siegel (1914-1996), perhaps after the element krypton) + -ite.]


informal something that renders a person or thing helpless: football movies are box-office kryptonite.
[C20: from the fictional substance to which the hero is vulnerable in the comic strip Superman]
References in periodicals archive ?
1 SHAKHTAR DONETSK found the Kryptonite to bring Pep Guardiola's supermen to their knees.
The Joker may be a little dark but it will put a smile on your face with its kiwi and apple mix, while Kryptonite is a gift to earth in the form of a refreshing green twist of lemon mint.
Star guard Paul Lee has been super the first two games of the semifinals series but in Game 3, he found his kryptonite in Barangay Ginebra's defense.
html) synopsis for the episode, titled "The Last Children of Krypton," Kara (Melissa Benoist) ends up seriously injured after a faceoff with Metallo (Frederick Schmidt) - a kryptonite powered villain tasked by CADMUS to wreak havoc in National City.
For South Shields' Haque, who won the Made4TheCage bantamweight strap last year, he is eager to put right wrongs from his last fight - a defeat - where he said he felt like he was hit with Superman's weakness kryptonite in the build-up.
We're not talking Teflon, we're talking Kryptonite.
like the walk home and its glass-strewn lots, glowing like kryptonite no
No, it's Superman - or should we say Supermen - pulled over after a Kryptonite out near Shirley on suspicion of driving with no insurance.
AMHERST -- It took a lot less than Kryptonite to fell this Man of Steel.
The poser put to frontman of '90s US hit-makers The Spin Doctors is does he still tire of trotting out the mega hits from Pocket Full Of Kryptonite - their 1991 debut album which sold 10 million copies and spawned such monster hits as Two Princes and Little Miss Understood?
CAN it really be 21 years since the release of the multi-million selling debut album Pocketful of Kryptonite, which reached number two in the UK charts, and launched the Spin Doctors around the globe?
Superman normally is more powerful than any human being, yet one little piece of kryptonite renders him helpless.