Albert Barnes Commentary Revelation 15:4

"Who shall not fear, O Lord, and glorify thy name? for thou only art holy; for all the nations shall come and worship before thee; for thy righteous acts have been made manifest." — Revelation 15:4 (ASV)

Who shall not fear thee, Lord. Reverence and adore Him; for the word fear, in the Scriptures, is commonly used in this sense when applied to God. The meaning here is that the judgments about to be inflicted on the beast and his image should and would teach people to reverence and adore God. Perhaps the idea of awe is also included here, since this would be the effect of punishment.

And glorify thy name. Honor Him—the name being used for the person who bore it. The meaning is that, as a consequence of these judgments, people would be brought to honor God and to acknowledge Him as the Ruler of the earth.

For thou only art holy. That is, in these judgments He would show Himself to be a holy God; a God hating sin, and loving righteousness and truth. When it is said that He only is holy, the expression is used, of course, in a comparative sense. He is so pure that it may be said that, in comparison with Him, no one else is holy. (Job 15:15).

For all nations shall come and worship before thee. That is, as the result of these punishments inflicted on this dread Antichristian power, they shall come and worship Him. Everywhere in the New Testament the destruction of that power is connected with the promise of the speedy conversion of the world.

For thy judgments are made manifest. Namely, on the beast. That formidable power is overthrown, and the grand hindrance to the universal spread of the true religion is now taken away! .