Men should be either treated generously or destroyed, because they take revenge for slight injuries – for heavy ones they cannot.

Niccolò Machiavelli

Revenge is an act of passion; vengeance of justice. Injuries are revenged; crimes are avenged.

Samuel Johnson

There are minds so impatient of inferiority that their gratitude is a species of revenge, and they return benefits, not because recompense is a pleasure, but because obligation is a pain

Samuel Johnson