God is one without a second, and the ordinary living entities are many without number. All such living entities are maintained by God Himself, and that is the verdict of the Vedic literatures
SB Canto 2
There is no doubt about Lord Kṛṣṇa's being the Supreme Lord, otherwise how was it possible for Him to kill a giant demon like Pūtanā when He was just on the lap of His mother, to overturn a cart with His leg when He was only three months old, to uproot a pair of arjuna trees, so high that they touched the sky, when He was only crawling? All these activities are impossible for anyone other than the Lord Himself.
One cannot manufacture a God by one's mental speculation or by numerical votes, as has become a practice for the less intelligent class of men. God is God eternally, and an ordinary living entity is eternally a part and parcel of God. God is one without a second, and the ordinary living entities are many without number. All such living entities are maintained by God Himself, and that is the verdict of the Vedic literatures. When Kṛṣṇa was on the lap of His mother, the demon Pūtanā appeared before His mother and prayed to nurture the child in her lap. Mother Yaśodā agreed, and the child was transferred onto the lap of Pūtanā, who was in the garb of a respectable lady. Pūtanā wanted to kill the child by smearing poison on the nipple of her breast. But when everything was complete, the Lord sucked her breast along with her very air of life, and the demon's gigantic body, said to be as long as six miles, fell down. But Lord Kṛṣṇa did not need to expand Himself to the length of the she-demon Pūtanā, although He was quite competent to extend Himself more than six miles long. In His Vāmana incarnation He posed Himself as a dwarf brāhmaṇa, but when He took possession of His land, promised by Bali Mahārāja, He expanded His footstep to the top of the universe, extending over thousands and millions of miles. So it was not very difficult for Kṛṣṇa to perform a miracle by extending His bodily feature, but He had no desire to do it because of His deep filial love for His mother, Yaśodā. If Yaśodā had seen Kṛṣṇa in her lap extending six miles to cope with the she-demon Pūtanā, then the natural filial love of Yaśodā would have been hurt because in that way Yaśodā would have come to know that her so-called son, Kṛṣṇa, was God Himself. And with the knowledge of the Godhood of Kṛṣṇa, Yaśodāmayī would have lost the temper of her love for Kṛṣṇa as a natural mother. But as far as Lord Kṛṣṇa is concerned, He is God always, either as a child on the lap of His mother, or as the coverer of the universe, Vāmanadeva. He does not require to become God by undergoing severe penances, although some men think of becoming God in that way. By undergoing severe austerities and penances, one cannot become one or equal with God, but one can attain most of the godly qualities. A living being can attain godly qualities to a large extent, but he cannot become God, whereas Kṛṣṇa, without undergoing any type of penance, is God always, either in the lap of His mother or growing up or at any stage of growth.
So at the age of only three months He killed the Śakaṭāsura, who had remained hidden behind a cart in the house of Yaśodāmayī. And when He was crawling and was disturbing His mother from doing household affairs, the mother tied Him with a grinding pestle, but the naughty child dragged the pestle up to a pair of very high arjuna trees in the yard of Yaśodāmayī, and when the pestle was stuck between the pair of trees, they fell down with a horrible sound. When Yaśodāmayī came to see the happenings, she thought that her child had been saved from the falling trees by the mercy of the Lord, without knowing that the Lord Himself, crawling in her yard, had wreaked the havoc. So that is the way of reciprocation of love affairs between the Lord and His devotees. Yaśodāmayī wanted to have the Lord as her child, and the Lord played exactly like a child in her lap, but at the same time played the part of the Almighty Lord whenever it was so required. The beauty of such pastimes was that the Lord fulfilled everyone's desire. In the case of felling the gigantic arjuna trees, the Lord's mission was to deliver the two sons of Kuvera, who were condemned to become trees by the curse of Nārada, as well as to play like a crawling child in the yard of Yaśodā, who took transcendental pleasure in seeing such activities of the Lord in the very yard of her home.
The Lord in any condition is Lord of the universe, and He can act as such in any form, gigantic or small, as He likes.