Avenge, revenge both imply to inflict pain or harm in return for pain or harm inflicted on oneself or those persons or causes to which one feels loyalty. The two words were formerly interchangeable, but have been differentiated until they now convey widely diverse ideas. Avenge is now restricted to inflicting punishment as an act of retributive justice or as a vindication of propriety: to avenge a murder by bringing the criminal to trial. Revenge implies inflicting pain or harm to retaliate for real or fancied wrongs; a reflexive pronoun is often used with this verb: Iago wished to revenge himself upon Othello.

Did you mean vengeful?