asurim yonim apanna
mudha janmani janmani
mam aprapyaiva kaunteya
tato yanty adhamam gatim
Attaining repeated birth amongst the species of demoniac life, O son of Kunti, such persons can never approach Me. Gradually they sink down to the most abominable type of existence.
Commentary by Srila Prabhupada
It is known that God is all-merciful, but here we find that God is never merciful to the demoniac. It is clearly stated that the demoniac people, life after life, are put into the wombs of similar demons, and, not achieving the mercy of the Supreme Lord, they go down and down, so that at last they achieve bodies like those of cats, dogs and hogs. It is clearly stated that such demons have practically no chance of receiving the mercy of God at any stage of later life. In the Vedas also it is stated that such persons gradually sink to become dogs and hogs. It may be then argued in this connection that God should not be advertised as all-merciful if He is not merciful to such demons. In answer to this question, in the Vedanta-sutra we find that the Supreme Lord has no hatred for anyone. The placing of the asuras, the demons, in the lowest status of life is simply another feature of His mercy. Sometimes the asuras are killed by the Supreme Lord, but this killing is also good for them, for in Vedic literature we find that anyone who is killed by the Supreme Lord becomes liberated. There are instances in history of many asuras—Ravana, Kamsa, Hiranyakasipu—to whom the Lord appeared in various incarnations just to kill them. Therefore God’s mercy is shown to the asuras if they are fortunate enough to be killed by Him.
Commentary by Sri Visvanatha Cakravarti Thakur
Not attaining me, the asuras attain low births. However, those asuras in the form of Kamsa and others attained me, Krishna, who appeared at the end of dvapara yuga in the twenty eighth cycle of Vaivasvata Manu’s reign. Though hating me, they attained me in the form of liberation. Because I am an ocean of mercy, I give even such sinful asuras liberation, which is only attained by the perfection of bhakti and jnana. The Personified Vedas say:
nibhrta-marun-mano’ksa drdha-yoga-yujo hrdi yan munaya upasate tad-arayo’pi yayuh smaranat
Simply by constantly thinking of Him, the enemies of the Lord attained the same Supreme Truth whom sages fixed in yoga worship by controlling their breath, mind and senses. SB 10.87.23
This widens the scope of my supreme attractive position which I mentioned previously.
But as the Bhagavatamrta Karika says:
mam krsna-rupinam yavan napnuvanti mama dvisah
tavad evadhamam yonim prapnuvantiti hi sphutam
In as much as those who hate me do not attain me in my form as Krishna, it is clear that they attain the lowest births.