Sri Gauranga Mahaprabhu

Lord Śrī Rāmacandra is so kind and merciful to His devotees that He is very easily satisfied by a little service rendered by anyone, human or not. This is the special advantage of worshiping Lord Rāmacandra, and there is the same advantage in worshiping Lord Śrī Caitanya Mahāprabhu. Lord Kṛṣṇa and Lord Rāmacandra, in the manner of kṣatriyas, sometimes showed Their mercy by killing asuras, but Lord Śrī Caitanya Mahāprabhu awarded love of God without difficulty even to the asuras. All the incarnations of the Supreme Personality of Godhead—but especially Lord Rāmacandra, Lord Kṛṣṇa and, later, Lord Śrī Caitanya Mahāprabhu—delivered many of the living entities present before Them, indeed almost all of them.
Śrī Caitanya Mahāprabhu is therefore represented in the six-armed form of ṣaḍ-bhūja-mūrti, which is a combination of Lord Rāmacandra, Lord Kṛṣṇa and Lord Śrī Caitanya Mahāprabhu. The best purpose of human life can be fulfilled by worshiping the ṣaḍ-bhūja-mūrti, the form of the Lord with six arms-two arms of Rāmacandra, two arms of Kṛṣṇa and two arms of Śrī Caitanya Mahāprabhu.
(SB 5.19.8 purport)

After this function at the house of Śrīvāsa Ṭhākura, Nityānanda Prabhu appeared, and when He met with Lord Caitanya He got the opportunity to see Him in His six-armed form.
PURPORT
The form of Ṣaḍ-bhuja, the six-armed Lord Gaurasundara, is a representation of three incarnations. The form of Śrī Rāmacandra is symbolized by a bow in one hand and an arrow in another, the form of Lord Śrī Kṛṣṇa is symbolized by a stick and a flute like those generally held by a cowherd boy, and Lord Caitanya Mahāprabhu is symbolized by a sannyāsa-daṇḍa and a kamaṇḍalu, or waterpot….
(CC Ādi 17.12)

One day Lord Caitanya Mahāprabhu exhibited to Lord Nityānanda Prabhu a six-armed form bearing a conchshell, disc, club, lotus flower, bow and flute.
(CC Ādi 17.13)