Usually Kryptonite . a fictional radioactive substance that is the only thing capable of hurting or weakening the otherwise invulnerable superhero Superman: Exposure to Kryptonite nullifies Superman's powers and immobilizes him with pain.
Sometimes Kryptonite . something that a person or thing cannot defend against or defeat; a nemesis or bête noire: The team has not found a way to stop the triple option attack, which has been their kryptonite over the last several years.Garlic oil is kryptonite for aphids.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use kryptonite in a sentence
And similar shards of enthusiasm-killing kryptonite are lodged in John Kasich, Mike Pence and Ted Cruz.
Thankfully, neither iteration relies on lazy storylines involving kryptonite or Lex Luthor (at least not yet).‘Man of Steel’ Is Fun to Watch, But It’s Still a Failure. Here’s Why. | Sujay Kumar | June 15, 2013 | THE DAILY BEAST
Interestingly, actual man-child Justin Bieber was cover kryptonite.
But for now, it looks like Republicans are surrounded by kryptonite.
Interesting juice choices like a liver detox or kryptonite mix flavors, like carrot and ginger with apple and grapefruit.
If you buy a kryptonite bike lock and it can be defeated with a Bic pen, you're not getting very good security for your money.Little Brother | Cory Doctorow