Krishna lists various objects or groups of living entities and states that He is their essence or the chief member of each group. It does not mean these objects and personalities are meant to be considered equal to Krishna. Rather, their prominence in our estimation is meant to remind us of Krishna and His opulence as Krishna is the source of everything and everyone.
Of the many-hooded Nāgas, Krishna is Ananta, and among the aquatics, He is the demigod Varuṇa. Of departed ancestors, He is Aryamā, and among the dispensers of law, He is Yama, the lord of death. (BG 10.29) Among the Daitya demons, He is the devoted Prahlāda; among subduers (kalayatām), He is time (kālaḥ); among beasts, He is the lion, and among birds, He is Garuḍa. (BG 10.30) Of purifiers, He is the wind; of the wielders of weapons, He is Rāma (Paraśurāma); of fishes, He is the shark, and of flowing rivers (srotasām), He is the Ganges. (BG 10.31) Of all creations, He is the beginning and the end and also the middle; of all education (vidyānāṁ), He is the spiritual education (adhyātma-vidyā), and among the stated claims (pravadatām), He is the conclusive truth (vādaḥ). (BG 10.32)
Of letters, Krishna is the letter A, and among compound words, He is the dual compound. Krishna alone (aham eva) is the inexhaustible time (akṣayaḥ kālo) and He is the all-facing (viśvato-mukhaḥ) creator (dhātā) – Brahmā. (BG 10.33) He is all-devouring death (mṛtyuḥ sarva-haraś cāham) and the generating principle (udbhavaś) of all that is yet to be (bhaviṣyatām). Of the feminine (nārīṇāṁ), He is fame (kīrtiḥ), beauty (śrīr), speech (vāk), memory (smṛtir), intelligence (medhā), steadfastness (dhṛtiḥ), and forgiveness (kṣamā). (BG 10.34) Of the hymns in the Sāma Veda, He is the Bṛhat-sāma (the great hymn), and of the metered chants (chandasām), He is the Gāyatrī. Of months, He is Mārgaśīrṣa [November-December], and of seasons, He is flower-bearing spring. (BG 10.35) He is the gambling (dyūtaṁ) of cheats (chalayatām), and of the splendid (tejasvinām), He is the splendor (tejas). He is the victory (jayo), He is the adventure (vyavasāyo), and He is the pure goodness (sattvaṁ) among all superior qualities (sattvavatām). (BG 10.36)