Most Helpful Guy
They take revenge in the wake and feel of self righteousness.
They feel the other person deserves it too because I suffered at your hands and therefore you have to suffer at my hands.
Not a good thinking that.
Most Helpful Girl
.. because they've been hurt or humiliated in someway , and they feel getting " even" by seeking revenge will help them to feel better--their emotional pain will lessen
The person who's been hurt looks on revenge as a form of establishing justice. They can't seem to gain control over their emotions , so act on their thoughts and emotions