In the second line the Lord is described as “the Almighty,” the same word that was used in Revelation 1:8, Revelation 4:8, and Revelation 11:17 to describe God (and again in Revelation 16:7, Revelation 16:14; Revelation 19:6, Revelation 19:15; Revelation 21:22). The term means literally all-powerful, omnipotent.
Given that he pours his wrath (and hence vengeance) on those who worship the dragon and his beasts (see Revelation 16:2), the title is clearly most fitting. In line with that title, God is tagged in the fourth line as “King of the nations.” Furthermore, toward the end of the song the prophecy is uttered that “all nations will come and worship you.”
3 And they sing the song of Moses, the servant of God, and the song of the Lamb, saying, “Great and amazing are your deeds, O Lord God the Almighty! Just and true are your ways, O King of the nations!