No other religious/spiritual text proclaims the supremacy of God as Bhagavad Gita does. In Bhagavad Gita, Krishna proclaims His supreme dominion as supreme God of all that be in a poetic and awe-inspiring manner. Arjuna who was the direct first-hand recipient of this knowledge conceded to the supremacy of Krishna after Krishna proclaimed His supremacy. Following, Arjuna himself glorifies Krishna in his own words as follows.
You are the supreme Brahman, supreme abode and ultimate purifier, the eternal divine Person and original God - unborn and almighty. All seers, such as Devarsi Narada, Asita, Devala and Vyasa, say this of you, and You in fact are personally telling me. Kesava, I accept as true all that You tell me. Neither gods nor demons know your personality, Lord. Only you yourself know your Self by your Self, O Supreme Person Who causes beings to be! God of gods! Master of the World! Kindly describe fully your vast, divine powers - powers by which You continue to pervade these worlds.
- literal translation of Bhagavad Gita 10.12-16 by HH H.D. Goswami