To the bitter end?

Bitterness – it consumes those in its grip.

Pastoral care Helen Thorne-Allenson

The jilted fiancée longing to make her ex look bad; the disgruntled employee fantasising about how to make his company pay; the former friend plotting to turn others against the one they used to trust – all because ‘it’s what they deserve’. Pain has been experienced and now the perpetrator must pay.