Albert Barnes on Revelation 19:15

And out of his mouth goeth a sharp sword. Rev 1:16. In that place the sword seems to be an emblem of his words or doctrines, as penetrating the hearts of men; here it is the emblem of a work of destruction wrought on his foes.

That with it he should smite the nations. The nations that were opposed to him; to wit, those especially who were represented by the beast and the false prophet, Rev 19:18-20.

And he shall rule them with a rod of iron. Rev 2:27; Rev 12:5.

And he treadeth the wine-press of the fierceness and wrath of Almighty God. This language is probably derived from Isa 63:1-4. See it explained in Barnes on "Isa 63:1", seq., and Barnes on "Re 14:19", Rev 14:20. It means here that his enemies would be certainly crushed before him--as grapes are crushed under the feet of him that treads in the wine-vat.

(i) "mouth" Rev 1:16 (k) "rod of iron" Ps 2:9