A.T. Robertson Commentary Revelation 19:21

"and the rest were killed with the sword of him that sat upon the horse, [even the sword] which came forth out of his mouth: and all the birds were filled with their flesh." — Revelation 19:21 (ASV)

The rest (ο λοιπο). Of the enemy (the kings and their hosts of verse 19).

Were killed (απεκτανθησαν). First aorist (effective) passive indicative of αποκτεινω. Those affected by the Caesar-worship (14:9ff.) were not at once cast into the lake with the two beasts.

Were filled (εχορτασθησαν). First aorist (effective) passive of χορταζω. As they had been invited to do in verse 17.