en_tn_condensed/rev/19/21.md

The rest of them were killed by the sword that came out of the mouth of the one who rode on the horse

This can be stated in active form. Alternate translation: "The rider of the horse killed the remainder of the beast's armies with the sword that extended from his mouth" (See: rc://en/ta/man/translate/figs-activepassive)

the sword that came out of the mouth

The sword blade was sticking out of his mouth. The sword itself was not in motion. See how you translated a similar phrase in Revelation 1:16.