'Revenge' traces to Latin 'vindicare' (to avenge) — kin to 'vindicate' and 'vendetta.'
The act of inflicting hurt or harm on someone in retaliation for a wrong or injury suffered at their hands.
From Old French 'revengier' (to avenge, to take vengeance), from Late Latin *revindic āre, a compound of Latin 're-' (back, again) + 'vindic āre' (to lay claim to, to avenge, to punish). Latin 'vindic āre' derives from 'vindex' (a claimant, an avenger, a champion), a word of uncertain further etymology, possibly containing 'vim' (accusative of 'vīs,' force, power) + 'dicere' (to say, to declare) — literally, one who declares force, one who asserts a claim by power. The same root
English has two words from the same Latin root that split along a moral axis: 'revenge' (personal, petty, self-serving) and 'avenge' (righteous, on behalf of others). The distinction is not etymological — both come from Latin 'vindic āre' — but was imposed by English usage over centuries to separate justified from unjustified retaliation.