kryptonite

noun

1. (figuratively, uncountable, usually)The one weakness of something or someone that is otherwise invulnerable.

   “The terrific seven-grain bread here is the kryptonite of restaurant reviewers: two mini-loaves and you are incapacitated.”

   “So while recording or sampling a Charlie Manson track […] makes for shock rock kudos aplenty, a devotion to Hubbard is kryptonite for credibility.”

   “We all have our own kryptonite or kryptonites, so don't tempt yourself by listening to so-called friends who are just demonic tools being used to bring you under.”

   “But of course porn is kryptonite to many investors.”

2. (slang, uncountable, usually)Crack cocaine.

verb

1. To expose to, or attack with, kryptonite.

   “And even those two were pretty puny, like Superman after he had been kryptonited.”

2. (figuratively)To destroy, wreck, or ruin; to affect adversely, as Superman is affected by kryptonite.