Adam Clarke on Revelation 19:11

A white horse - This is an exhibition of the triumph of Christ after the destruction of his enemies. The white horse is the emblem of this, and Faithful and True are characters of Christ. See Rev 3:14.

In righteousness he doth judge and make war - The wars which he wages are from no principle of ambition, lust of power, or extension of conquest and dominion; they are righteous in their principle and in their object. And this is perhaps what no earthly potentate could ever say.