Vengeance is an action made by an individual who has been physically or psychologically hurted and who’s giving the same treatment to the one who made them suffer so they can be punished. It’s a primitive and natural defense mechanism, we all feel this sensation at some point in our life. Vengeance is often an impulse.
The wish to avenge can appear in multiple situations : when one has been assaulted, or humiliated, when one’s partner cheated on them or broke up with them, when losing an important game...
Vengeance comes from feelings of anger, of injustice (see justice), of pain but also when one prefers to strike back rather than forgiving.
One may consider that vengeance, a negative emotion, may have positive consequences on the one who’s avenging : it allows them to relieve their pain, to get justice, to feel powerful (see power),...
However those feelings are only temporary and can be quickly replaced by remorses and sadness because hurting someone who hurted us doesn’t make the pain go away and we steep to their level.