Genesis 3:22
¶ And the Lord God said, Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever:
Who is “us”.
The Trinity - but you knew that didn’t you?
:)
Take your pick: Some commentators believe God was referencing the family of heaven -- as this all happened after some angels sinned, thus the clan of angels then knew both good and evil. Therefore, "us" could be both God and His angels -- and He could have been speaking to His angels.
More commentators believe God is speaking of Himself -- a diverse Personhood within the unity of one God. Trinitarians have no problem with the concept of "us" within the Godhood -- as God is a compound unity and our world is a diversity-within-unity.
Look around you, the world is full of that arrangement! Having plural species of animals doesn't negate the oneness of the animal world, does it? Having two genders doesn't negate the oneness of humankind, does it?
Let's face it, before angels existed an "us" AND a "Him" existed simultaneously! Love is social. The "diversity" of God is the "us" -- the social -- the relational component of Who He is. The Oneness of God is the unity; the bonding; the 3-cord rope that can't be separated; the intimacy; the single nature.
(Besides, OMM, even Mormons say there's an "us" in the one "Godhead"...so even Mormons try to at times sound a bit "trinitarian" 'cause it makes them appear more orthodox and it helps explain key NT passages...and the Book of Mormon is chalk full of trinitarian passages!)