The supremacy of Lord Visnu is confirmed in Bhagavad-gita (BG 10.12) in this statement by Arjuna: You are the primal God, transcendental and original, and You are the unborn and all-pervading beauty

Expressions researched:
"You are the primal God, transcendental and original, and You are the unborn and all-pervading beauty"

Srimad-Bhagavatam

SB Canto 10.1 to 10.13

"You are the Supreme Brahman, the ultimate, the supreme abode and purifier, the Absolute Truth and the eternal divine person. You are the primal God, transcendental and original, and You are the unborn and all-pervading beauty".

SB 10.1.20, Translation and Purport

After reaching the shore of the ocean of milk, the demigods worshiped the Supreme Personality of Godhead, Lord Viṣṇu, the master of the whole universe, the supreme God of all gods, who provides for everyone and diminishes everyone's suffering. With great attention, they worshiped Lord Viṣṇu, who lies on the ocean of milk, by reciting the Vedic mantras known as the Puruṣa-sūkta.

The demigods, such as Lord Brahmā, Lord Śiva, King Indra, Candra and Sūrya, are all subordinate to the Supreme Personality of Godhead. Aside from the demigods, even in human society there are many influential personalities supervising various businesses or establishments. Lord Viṣṇu, however, is the God of gods (parameśvara). He is parama-puruṣa, the Supreme Being, Paramātmā. As confirmed in the Brahma-saṁhitā (BS 5.38), īśvaraḥ paramaḥ kṛṣṇaḥ sac-cid-ānanda-vigrahaḥ: "Kṛṣṇa, known as Govinda, is the supreme controller. He has an eternal, blissful, spiritual body." No one is equal to or greater than the Supreme Personality of Godhead, and therefore He is described here by many words: jagannātha, deva-deva, vṛṣākapi and puruṣa. The supremacy of Lord Viṣṇu is also confirmed in Bhagavad-gītā (BG 10.12) in this statement by Arjuna:

paraṁ brahma paraṁ dhāma

pavitraṁ paramaṁ bhavān

puruṣaṁ śāśvataṁ divyam

ādi-devam ajaṁ vibhum

"You are the Supreme Brahman, the ultimate, the supreme abode and purifier, the Absolute Truth and the eternal divine person. You are the primal God, transcendental and original, and You are the unborn and all-pervading beauty." Kṛṣṇa is ādi-puruṣa, the original Personality of Godhead (govindam ādi-puruṣaṁ tam ahaṁ bhajāmi). Viṣṇu is a plenary expansion of Lord Kṛṣṇa, and all the viṣṇu-tattvas are parameśvara, deva-deva.