Text 18 

yasmat ksharam atito ’ham
aksharad api cottamah
ato ’smi loke vede ca
prathitah purushottamah 

Translation

Because I am transcendental, beyond both the fallible and the infallible, and because I am the greatest, I am celebrated both in the world and in the Vedas as that Supreme Person. 

Commentary by Srila Prabhupada 

No one can surpass the Supreme Personality of Godhead, Krishna—neither the conditioned soul nor the liberated soul. He is therefore the greatest of personalities. Now it is clear here that the living entities and the Supreme Personality of Godhead are individuals. The difference is that the living entities, either in the conditioned state or in the liberated state, cannot surpass in quantity the inconceivable potencies of the Supreme Personality of Godhead. It is incorrect to think of the Supreme Lord and the living entities as being on the same level or equal in all respects. There is always the question of superiority and inferiority between their personalities. The word uttama is very significant. No one can surpass the Supreme Personality of Godhead. 

The word loke signifies “in the paurusa agama (the smriti scriptures).” As confirmed in the Nirukti dictionary, lokyate vedartho ’nena: “The purpose of the Vedas is explained by the smriti scriptures.” 

The Supreme Lord, in His localized aspect of Paramatma, is also described in the Vedas themselves. 

The following verse appears in the Vedas (Chandogya Upanishad 8.12.3): tavad esa samprasado ’smac charirat samutthaya param jyoti-rupam sampadya svena rupenabhinispadyate sa uttamah purushah. “The Supersoul coming out of the body enters the impersonal brahmajyoti; then in His form He remains in His spiritual identity. That Supreme is called the Supreme Personality.” This means that the Supreme Personality is exhibiting and diffusing His spiritual effulgence, which is the ultimate illumination. That Supreme Personality also has a localized aspect as Paramatma. By incarnating Himself as the son of Satyavati and Parashara, He explains the Vedic knowledge as Vyasadeva.

Commentary by Sri Visvanatha Cakravarti Thakur

Having spoken about the object of worship of the yogis, paramatma, the Lord now speaks about the object of worship of the devotees, bhagavan.Though he in his form as Krsna is bhagavan himself, he denotes the supreme excellence of his own svarupa as Krsna using the name purusottama, he who is superior (uttama) to the paramatma (purusa). I am superior to the jiva (ksaram), and I am superior to the brahman (aksarat), and also to the unchanging person, paramatma (purusa).

yoginam api sarvesam mad-gatenantar-atmana
sraddhavan bhajate yo mam sa me yuktatamo matah

Of all yogis, he who, absorbing his mind in me, worships me with faith, is considered by me to be the best yogi.   BG 6.47

From the difference in the worshipper, one can conclude that there is a difference in the worshipable object. The word ca in the verse also indicates that Krsna is superior even to the Lord of Vaikuntha and others. This is understood from the words of Suka:

ete camsa-kalah pumsah krsnas tu bhagavan svayam

These are all parts or parts of parts. Krsna is bhagavan himself.    SB 1.3.28

Though his one sac cid ananda form is called by the names brahman,   paramatma   and   bhagavan,   actually   there   is   no difference at all between them, svarupa dvaydbhavat: there is no duality in your form. (SB 6.9.36) However, because of observing difference in the worshippers, in terms of sadhana and the results, difference has been designated.  That is to say, the sadhana respectively of the jnani, yogi and bhakta produces realization of brahman, paramatma and bhagavan. The result of jnana and yoga is mere liberation, and the result of bhakti is to become an associate of the Lord with prema. Also without bhakti, the jnanl and yogi do not even attain liberation. This is understood from the following verses:

naiskarmyam apy acyuta-bhava-varjitam na sobhate

Knowledge of self-realization, even though free from all material affinity, does not look well if devoid of a conception of the Infallible [God]. SB 1.5.12

pureha bhuman bahavo 'pi yoginas
tvad-arpiteha nija-karma-labdhaya
vibudhya bhaktyaiva kathopanitaya
prapedire 'njo 'cyuta te gatim param

O almighty Lord, in the past many yogis in this world achieved the platform of devotional service by offering all their endeavors unto You and faithfully carrying out their prescribed duties. Through such devotional service, perfected by the processes of hearing and chanting about You, they came to understand You, O infallible one, and could easily surrender to You and achieve Your supreme abode. SB 10.14.5

The worshippers of brahman and paramatma must necessarily perform bhakti to bhagavan in order to achieve the final results of their sadhana. The worshippers of bhagavan however do not perform worship of brahman or paramatma to achieve the results of their sadhana.

tasman mad-bhakti-yuktasya yogino vai mad-atmanah
na jnanam na ca vairagyam prayah sreyo bhaved iha

Therefore, for a devotee engaged in My loving service, with mind fixed on Me, the cultivation of knowledge and renunciation is generally not the means of achieving the highest perfection within this world. SB 11.20.31

yat karmabhir yat tapasa jnana-vairagyatas ca yat
yogena dana-dharmena sreyobhir itarair api

sarvam mad-bhakti-yogena mad-bhakto labhate 'njasa
svargapavargam mad-dhama kathancid yadi vanchati

Everything that can be achieved by fruitive activities, penance, knowledge, detachment, mystic yoga, charity, religious duties and all other means of perfecting life is easily achieved by My devotee through loving service unto Me. If somehow or other My devotee desires promotion to heaven, liberation, or residence in My abode, he easily achieves such benedictions. SB 1.20.31-32

ya vai sadhana-sampattih purusartha-catustaye
taya vina tad apnoti naro narayanasrayah

Even without the usual requirements for achieving the perfection of life, a person will gain that perfection if he is simply a surrendered devotee of Narayana Narayaniya

Therefore, by worship of bhagavan, it is possible to attain all of the results: material enjoyment, liberation and prema. But by the worship of brahman and paramatma alone, it is not possible to attain enjoyment, liberation or prema. Therefore, it is said that bhagavan is in a superior position even though he is not different from brahman and paramatma. It is just as the huge fire is considered superior among a small light, a lamp and a huge fire, because of its superior ability to alleviate the pain of cold, even though all the items are essential the same energy.

However, among the forms of bhagavan, Krsna is considered to be the supreme attractive, just as the sun is considered superior to the huge fire. Why? Because Krsna alone gave nirvana moksa, the final fruit of worship of brahman, even to his enemies such as Agha, Baka and Jarasandha, who were most sinful. This verse has been explained according to Sridhara Svami's commentary on the verse brahmano hi pratisthaham.

Madhusudana Sarasvati says:

Men skilful at pious work worship Krsna repeatedly, who appears continually to relieve the burden of the earth, who enables the intelligent to cross the material ocean, who is the delight of the women of Vraja, the essence of the beauty of the rain cloud as described in the Vedas, and the form of knowledge and bliss.

I do not know any truth higher than Krsna, who has lotus eyes, a face beautiful as the full moon, and lips red like the bimba fruit; who has the complexion of a rain cloud; who wears yellow cloth; and who holds a flute in his hand. Madhusudana Sarasvati's commentary on verse 19

Those fools who cannot tolerate the glories of Krsna which have been ascertained with valid proof go to hell. Madhusudana Sarasvati's commentary on verse 20

There should be no indignation at the explanation of these three verses (16-18) which establish the supreme position of the form of Krsna, with all due respects to the impersonalists.