The God of the Bible is the supreme creator of our ordered world.
He is utterly unrivaled in his role as God over all.
His name is Yahweh, which implies that he is the existing one, the one who always is.
Thousands of times the Bible employs singular pronouns for God, which strongly implies he is a singular person.
Four times, God says “us,” which likely resulted from him talking to other members of his divine counsel.