Unforgivable (adjective)

Not able to be excused or pardoned; not able to be forgiven; unpardonable.

Origin:

From un- (not) + forgivable (able to be forgiven, able to be excused or pardoned).

Examples:

1. His actions were unforgivable and he was fired from his job.
2. The betrayal was unforgivable and the friendship was over.
3. The crime was unforgivable and the perpetrator was sentenced to life in prison.
4. The mistake was unforgivable, it cost the company millions of dollars.
5. The insult was unforgivable and the two nations severed diplomatic ties.