a·venge 
(ə-vĕnj)
(ə-vĕnj)tr.v. a·venged, a·veng·ing, a·veng·es
1. To inflict a punishment or penalty in return for; revenge: avenge a murder.
2. To take vengeance on behalf of: avenged their wronged parents.
[Middle English avengen, from Old French avengier : a-, to (from Latin ad-; see AD-) + vengier, to vindicate (from Latin vindicāre, to claim; see VINDICATE).]
a·venger n.
a·venging·ly adv.