Remorse
Etymology
From Medieval Latin "remorsus," from Latin "remordere" (to bite back, to bite again), from re- (back) and "mordere" (to bite) — the root that also gives "morsel." The vivid image is of conscience biting at you, gnawing after the fact. English took it up in the fourteenth century with that sense of a repeated, inner sting.
noun · /rih-MORS/
Deep, painful regret and self-reproach for having done wrong.
What it names
The moral bite of conscience after a wrong — sharper than regret because it accuses the self.
Example
He felt no remorse for winning, only for the careless words that had cost him a friend.
Related idea
Regret merely wishes things had gone differently; remorse adds moral self-reproach — the sting of having done wrong, not just of things turning out badly.