l'impair

Mais aussi malheureux que vous soyez, faites un impair et vous êtes fichu.

But no matter how unhappy you are, make one mistake and you're done for.

— Stalker (1979)

Il a commis un impair quand il a demandé si elle était enceinte.

He made a mistake when he asked if she was pregnant.

J'ai commis un grave impair.

I made a serious blunder.

Il devait avoir le trac, mais il n'a commis aucun impair.

He must have been nervous, but he didn't put a foot wrong.

— Titanic (1997)