What words refer to getting revenge?

revenge, get revenge, take revenge, in revenge, avenge, get back at, get even with, pay back, repay, requite, retaliate, in retaliation, retribution, wreak vengeance, I'll get you for this, be out to get,

What words refer to a person who gets revenge?

avenger, nemesis,

What words refer to a situation in which both people have done something bad to each other?

be even, be quits,