Synonyms for Retaliate:

n.

respond in kind, pay back, get your own back, settle an (old) score (with someone), get back at, get/be even (with someone). hit back, forgiveness, attack. counter (noun)
requite.
retaliate (noun)
strike back, revenge, avenge.

v.

atone (verb)
appease, recompense, atone, redress, make amends, rectify, restitute, compensate, redeem.
get even with someone (verb)
strike back, recompense, revenge, repay, get back at, reciprocate, pay back, requite.
retaliate (verb)
countercharge, return fire, reprise, counterblow, Retribute, retort, avenge, reciprocate, respond, counteract, counter, revenge, repay, exchange.
revenge (verb)
punish.

Other synonyms:

get back at, hit back. pay back. answer
retort.
recompense
make amends.
Other relevant words:
requite, get back at, strike back, hit back, pay back.

Usage examples for retaliate

  1. The Redskins are not all bad; and many, I fear, have been driven, by the ill treatment they have received from white men, to retaliate and have obtained a worse character than they deserve." – In the Rocky Mountains by W. H. G. Kingston
  2. How they were a childlike race, credulous and trustful, but, like all credulous and trustful people, given to retaliate when imposed upon with a larger insincerity, exaggeration, and treachery. – Susy, A Story of the Plains by Bret Harte