impardonnable

C'était impardonnable.

That was unforgivable.

C'est impardonnable de fréquenter un gueux pareil, ma chérie !

It's unforgivable to date such a broken man, darling!

Un tel comportement de sa part est impardonnable.

I can't forgive him for behaving like that.

S'il y a une chose impardonnable, c'est de ne pas pardonner.

If there is such a thing as an unforgivable act, it is the act of not forgiving.

C'était une erreur impardonnable.

That was an unforgivable error.

Son crime est impardonnable.

His crime is unforgivable.