SB 2.7.27: It’s impossible for anyone else to take the life of a huge demon, while just an infant; to kick over a big cart, while just three months old; or to uproot two huge arjuna trees just by crawling in between them.
There’s an obvious meaning here, and another, not-so-obvious one. The obvious one is that no ordinary human being can do these things. No ordinary infant can even protect itself, what to speak of kill a giant demon who attacks it. The cart was not a hand cart, it was like a child today kicking over a car. Not that dramatic, but similar – carts in those days were like cars. And Arjuna trees (Terminalia Arjuna) are notoriously tall (20-25 meters) and have very strong bases and roots.
The not-so-obvious meaning is that Brahmājī is not simply saying “no mortal can do this” – this śloka comes in the middle of a summary of avatāra – So, Brahmā is also saying, “no other avātar displays deeds as amazing as Krishna does.”
Viśvanātha Cakravartī elaborates: Vāmana was also a small child who defeated a huge, powerful demon – but he transformed into a huge, powerful form to do so. Krishna did not kill the giant Pūtana in this manner, he remained as a vulnerable infant. Why? It is more sweet. There is less awe and reverence. If Krishna transformed into a huge superhero to kill Pūtana, that would have intruded into the loving mood of his parents. He valued their love more than the killing of the demon, so he remained in the shape they adored, and coincidentally got the work done of getting rid of Pūtana in a beautiful way.
Nṛsiṁha kicked open a huge pillar – and Krishna kicked over a big cart. But Nṛsiṁha did so using huge, fearsome feet. Krishna kicked over the cart with the tiny foot of a three-month old child. Why? Same reason as explained above.
Varāha picked up the huge earth from the depths, but Krishna knocked down the huge trees and uprooted them from their depths. Varāha had to become a gigantic boar with huge, powerful tusks to accomplish his task, but Krishna didn’t have to become a gigantic boar, or even a huge super-baby to knock over these ultra-formidable trees. He just crawled in between them.
So, no other avatāra can match Krishna in sweetness.
Two ślokas later [2.7.29] Brahmā will mention how Krishna saved the Vrajavāsīs from a forest fire. To do this he had to do “godlike deeds” (divya karma), so he first instructed all the Vrajavāsīs to close their eyes, so as not to disturb the sweetness of their affection for him.