A.T. Robertson Commentary Revelation 19:12

"And his eyes [are] a flame of fire, and upon his head [are] many diadems; and he hath a name written which no one knoweth but he himself." — Revelation 19:12 (ASV)

A flame of fire (φλοξ πυρος). As in the opening vision of Christ in 1:14 (2:18).

Many diadems(διαδηματα πολλα). A new feature, but the dragon has a diadem on each of his seven heads (12:3) and the first beast one upon each of his ten horns (13:1). So the victorious Messiah will wear many royal diadems and not mere crowns, because he is King of kings (19:16).

And he hath (κα εχων). Nominative active present participle of εχω either used absolutely as an independent verb (like indicative) or in an anacoluthon, though αυτου (his) is genitive.

A name written (ονομα γεγραμμενον). Perfect passive participle of γραφω as in 2:17 (cf. 3:12).

But he himself (ε μη αυτος). "Except himself" (common ellipsis of the verb after ε μη, "if not"). See 2:17; 3:12 for the new name there described. See 14:1 for the name of Christ on the forehead of the 144,000, and 17:5 for the name on the forehead of the harlot. This word here supplements what Jesus says in Mt 11:27.