Albert Barnes Commentary Psalms 76:7

"Thou, even thou, art to be feared; And who may stand in thy sight when once thou art angry?" — Psalms 76:7 (ASV)

You, even you, are to be feared - To be held in reverence or veneration. The repetition of the word “you” is emphatic, as if the mind paused at the mention of God, and remained in a state of reverence, repeating the thought. The particular “reason” suggested here why God should be held in reverence was the display of his power in overthrowing by a word the mighty hosts that had come against the holy city.

And who may stand in your sight - Who can stand before you? implying that no one had the power to do it. When once you are angry. If such armies have been overcome suddenly by your might, then what power is there which could successfully resist you?