John Gill Commentary Revelation 19:2

"for true and righteous are his judgments; for he hath judged the great harlot, her that corrupted the earth with her fornication, and he hath avenged the blood of his servants at her hand." — Revelation 19:2 (ASV)

For true and righteous are his judgments
As in (See Gill on Revelation 15:3), (See Gill on Revelation 16:7): this is to be understood of God's judgments in general, and is a reason of the attribution of praise and glory to him; which may be said to be true, because, being threatened, are now fulfilled; and to be "righteous", because according to the demerit of sin; and particularly God's judgments on antichrist are intended:

for he has judged the great whore ;
Jezebel, Babylon, the Romish antichrist, before spoken of, (Revelation 17:1) not only by passing a sentence of condemnation on her, but by executing it, putting it into the hearts of the kings to hate and burn her, and utterly destroy her; and which is judging right, since it follows:

which did corrupt the earth with her fornication ;
drew the kings and inhabitants of the Roman empire into wicked and idolatrous practices, and so corrupted and destroyed them in soul, body, and estate; (See Gill on Revelation 11:18) for this vision is contemporary with the seventh trumpet:

and has avenged the blood of his servants at her hand ;
shed by her, (Revelation 18:20Revelation 18:24) (16:6) and this being done in righteous judgment, is matter of joy and praise to the saints.