Jamieson, Fausset and Brown on Revelation 19:2

2. which did corrupt the earth--Greek, "used to corrupt" continually. "Instead of opposing and lessening, she promoted the sinful life and decay of the world by her own earthliness, allowing the salt to lose its savor" [Auberlen].

avenged--Greek, "exacted in retribution." A particular application of the principle (Ge 9:5).

blood of his servants--literally shed by the Old Testament adulterous Church, and by the New Testament apostate Church; also virtually, though not literally, by all who, though called Christians, hate their brother, or love not the brethren of Christ, but shrink from the reproach of the cross, and show unkindness towards those who bear it.