Its in the Silmarillion Gothmog. LoL You died there.
Of the deeds of desperate valour there done, by the chieftains of the noble houses and their warriors, and not least by Tuor, much is told in The Fall of Gondolin: of the battle of Ecthelion of the Fountain with Gothmog Lord of Balrogs in the very square of the King, where each slew the other, and of the defence of the tower of Turgon by the people of his household, until the tower was overthrown; and mighty was its fall and the fall of Turgon in its ruin. - Sil
I doubt the Elves would consider it a battle if Ecthelion just ambushed Gothmog from behind.
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Therefore I say that we will go on, and this doom I add: the deeds that we shall do shall be the matter of song until the last days of Arda
