The Greek verb “ἐκδικέω”

Limited to Lk. 18:3, 5; Rom. 12:19; 2 Cor. 10:6; Rev. 6:10; 19:2, the Greek verb “ekdikeo” meant “punish” or “take revenge.”  John used this verb to describe God taking vengeance on evil earthly powers.  Paul used this word in 2 Cor. 10:6 to say disobedience will be punished.  In Rom. 12:19, this word is used to say private acts of vengeance are prohibited.  Luke used this term to relate Jesus’ teaching about the parable of an unjust judge.