Albert Barnes on Revelation 18:1

And after these things. After the vision referred to in the previous chapter.

I saw another angel come down from heaven. Different from the one that had last appeared, and therefore coming to make a new communication to him. It is not unusual in this book that different communications should be entrusted to different angels. Compare Rev 14:6,8-9,15,17-18.

Having great power. That is, he was one of the higher rank or order of angels.

And the earth was lightened with his glory. The usual representation respecting the heavenly beings. Compare Ex 24:16, Mt 17:2, Lk 2:9 Acts 9:3. This would, of course, add greatly to the magnificence of the scene.

(a) "glory" Eze 43:2