The Greek text says literally that one
mighty angel picked up a stone. The emphasis on one angel doing the work here is not meant to belittle Babylon (as if she is not so great
after all) but is meant to underscore the strength of God’s servants. As is fitting for the King of kings, each of his servants is sufficiently mighty by themselves to deal appropriately with the Lord’s defeated enemy.
21 Then a mighty angel took up a stone like a great millstone and threw it into the sea, saying, “So will Babylon the great city be thrown down with violence, and will be found no more;