In the verses below is a direct proof given by none other but Krsna das Kaviraj Goswami who claims again and again that all spiritual success he attained was solely due to mercy of Lord Nityananda. He cannot stop glorifying Lord Nityananda, so his words flow and flow and flow… All glories to Nityananda-Rama! Now even this sinful worm in stool as myself has hope for deliverance due to His mercy only!
From Sri Caitanya Caritramrita, Adi lila, chapter 5
“All glory, all glory to Lord Nityānanda Balarāma, by whose mercy I have attained shelter in the transcendental abode of Vṛndāvana. All glory, all glory to the merciful Lord Nityānanda, by whose mercy I have attained shelter at the lotus feet of Śrī Rūpa and Śrī Sanātana. By His mercy I have attained the shelter of the great personality Śrī Raghunātha dāsa Gosvāmī, and by His mercy I have found the refuge of Śrī Svarūpa Dāmodara. By the mercy of Sanātana Gosvāmī I have learned the final conclusions of devotional service, and by the grace of Śrī Rūpa Gosvāmī I have tasted the highest nectar of devotional service. All glory, all glory to the lotus feet of Lord Nityānanda, by whose mercy I have attained Śrī Rādhā-Govinda.
I am more sinful than Jagāi and Mādhāi and even lower than the worms in the stool. Anyone who hears my name loses the results of his pious activities. Anyone who utters my name becomes sinful. Who in this world but Nityānanda could show His mercy to such an abominable person as me? Because He is intoxicated by ecstatic love and is an incarnation of mercy, He does not distinguish between the good and the bad. He delivers all those who fall down before Him. Therefore He has delivered such a sinful and fallen person as me. Although I am sinful and I am the most fallen, He has conferred upon me the lotus feet of Śrī Rūpa Gosvāmī.
The mercy of Lord Nityānanda showed me Śrī Madanamohana and gave me Śrī Madanamohana as my Lord and master. He granted to one as low as me the sight of Lord Govinda. Words cannot describe this, nor is it fit to be disclosed.
Therefore who can describe the mercy of the lotus feet of Him [Lord Nityānanda] by whom I have attained the shelter of this Lord Govinda? All the groups of Vaiṣṇavas who live in Vṛndāvana are absorbed in chanting the all-auspicious name of Kṛṣṇa. Lord Caitanya and Lord Nityānanda are their life and soul. They do not know anything but devotional service to Śrī Śrī Rādhā-Kṛṣṇa. The dust and shade of the lotus feet of the Vaiṣṇavas have been granted to this fallen soul by the mercy of Lord Nityānanda. Lord Nityānanda said, “In Vṛndāvana all things are possible.”
Here I have explained His brief statement in detail. I have attained all this by coming to Vṛndāvana, and this was made possible by the mercy of Lord Nityānanda. I have described my own story without reservations. The attributes of Lord Nityānanda, making me like a madman, force me to write these things. The glories of Lord Nityānanda’s transcendental attributes are unfathomable. Even Lord Śeṣa with His thousands of mouths cannot find their limit.” [CC Adi 5.200-210; 216-217; 227-234]