How many times did Krishna show his Vishnu (four-handed) form and to whom?

 Krishna manifested his Vishnu (four-handed) form multiple times in the Mahabharata and Srimad Bhagavatam. Here are the significant instances:

1. To Vasudeva (At Birth)

Verse (Srimad Bhagavatam 10.3.9-10):

"Vasudeva saw that wonderful child of lotus-like eyes, endowed with four arms, bearing a conch, wielding a mace and a discus; having the Srivatsa mark on his chest, the Kaustubha gem, and clad in yellow silken garments, possessing the complexion of a rain-bearing cloud."

2. To Devaki (After Kamsa’s Death)

Verse (Srimad Bhagavatam 10.85.17-18):

"O mother, in my previous birth I appeared as Prishnigarbha to you and in this life as your son. To remove your doubts, I shall now reveal my original divine form."

Having spoken thus, Krishna manifested his four-armed form, adorned with the conch, disc, mace, and lotus. Seeing this form, Devaki was filled with awe and devotion."

3. To Muchukunda (After Burning Kalayavana)

Verse (Srimad Bhagavatam 10.51.16-23):

"Muchukunda saw Krishna before him, effulgent like the rising sun, dressed in yellow silken garments, possessing four arms, and appearing like a dark-blue raincloud."

4. To Sage Markandeya (During Cosmic Deluge)

Verse (Srimad Bhagavatam 12.9.30-34):

"Markandeya saw that child (Krishna) sucking His toe, radiant like a dark-blue lotus. Soon after, he saw the same Lord in His four-armed Vishnu form, holding the conch, discus, mace, and lotus."

5. To Ghantakarna (The Pishacha)

Verse (Harivamsa, Bhavishya Parva, Chapter 81):

"Then the terrible Pishacha saw Keshava, Hari, in his own soul, wearing yellow silk clothes, having lotus-like eyes, and dark blue complexion. Vishnu was holding the conch, chakra, garland, and mace, wearing a crown, the Kaustubha gem, and the Srivatsa mark on his chest. Seeing this divine form, the Pishacha considered himself to have achieved the ultimate goal."

6. To Arjuna (During the Bhagavad Gita) - Mahabharata (Bhagavad Gita Parva, Chapter 11, Verse 46-50)

Verse (Bhagavad Gita 11.46):

"O Lord of the gods! O abode of the universe! Be merciful. I wish to see your earlier form, crowned, with a mace and chakra in hand. O thousand-armed one! O universal form! Become manifest in your four-armed form."

Verse (Bhagavad Gita 11.50):

"The Supreme Lord, assuming His four-armed form, then appeared in His gentle two-armed form, thus pacifying the frightened Arjuna."

7. To Brahma (During the Brahma-Vimohana Lila)

Verse (Srimad Bhagavatam 10.14.19-22):

"Brahma saw the Supreme Lord in each cowherd boy and calf, appearing in four-armed form as Vishnu, adorned with golden helmets, yellow garments, conch, disc, mace, and lotus."

8. To the Gopis (During the Rasa Lila)

Verse (Gopala-Tapani Upanishad 1.28-30):

"The Supreme Lord Krishna, who is the source of all Vishnu forms, briefly assumed his four-armed form, but upon Radha's approach, he resumed his original two-armed form."

9. Bhishma Saw Krishna’s Four-Armed Form at His Death

Verse (Mahabharata, Anushasana Parva 167.43-44):

"I seek refuge in that Krishna, who is the Supreme Soul of the Universe, the Immutable One, the Vishnu of the Vedas, the All-pervading Lord."

"As Bhishma left his mortal body, he beheld Krishna standing before him in his four-armed form, holding the conch, discus, mace, and lotus. He realized that Krishna was indeed the Supreme Being, Vishnu himself."