G1558
ἔκδικος
avenging
ἔκδικος, -ον (δίκη), [in LXX: Wis.12:12, Sir.30:6, 4Ma.15:29 * ;] __1. without law, unjust. __2. exacting penalty from; as subst., an avenger: Rom.13:4; before περί, 1Th.4:6 (in π., a legal representative; Milligan, Th., l.with).† (AS)
The KJV translates G1558 in the following manner:
avenger (2x), revenger (2x)
Full Thayer's lexicon entry
ἔκδικος — ékdikos
ἔκδικος, ἔκδικον (δίκη right, justice, penalty);
1. "without law and justice (cf. Latinexlex), unjust": Aeschylus, Sophocles, Euripides, Aelian n. an. 16, 5.
2. exacting penalty from (ἐκ) one; an avenger, punisher: Rom 13:4; περί τίνος, 1Th 4:6; (Wis 12:12; Sir 30:6; 4Ma 15:26 (29); (Plutarch, de garrul. § 14, p. 509 f.); Herodian, 7, 4, 10 (5th edition, Bekker; others)).
2 occurrences
Romans (1), I Thessalonians (1)