Source : Webster's Revised Unabridged Dictionary (1913)

Avenger \A*ven"ger\, n.
   1. One who avenges or vindicates; as, an avenger of blood.

   2. One who takes vengeance. [Obs.] --Milton.

Source : WordNet®

avenger
     n : someone who takes vengeance [syn: {retaliator}]