the.com/unforgiveness
Drinking poison and waiting for the other person to die.
means The state of holding onto resentment toward someone who wronged you, refusing to let the grudge go.
from From Old English forgiefan, to give up or grant a pardon, with the negating un- bolted on top — literally the refusal to give it up.
Body countChronic grudges raise blood pressure and stress hormones.
Not in dictionariesForgiveness gets the entry; its shadow rarely does.
Self-targetingThe grudge-holder suffers far more than the offender.