The term itself means that the Lord our God has (literally) all power. Nothing in the entire universe falls outside his control. The wider context obliges us to understand that this includes the prostitute, the beast upon which she rides, the kings of the earth, yes, every civilization or state or culture that humanity may cobble together under any diabolic influence. On the cross of Calvary, Christ Jesus disarmed all rulers and authorities (Colossians 2:15), and upon his ascension he received a throne far above all rule and authority and power and dominion in this age and the age to come (Ephesians 1:21–22). In fact, this was precisely the blessed reality heaven confessed in Revelation 5:12 and earth echoed in Revelation 5:13.
6 Then I heard what seemed to be the voice of a great multitude, like the roar of many waters and like the sound of mighty peals of thunder, crying out, “Hallelujah! For the Lord our God the Almighty reigns.