ātmānam iha sañjātaṁ
jānan prāg viṣṇunā hatam
mahāsuraṁ kālanemiṁ
yadubhiḥ sa vyarudhyata
ātmānam - personally; iha - in this world; sañjātam - born again; jānan - understanding well; prāk - previously, before this birth; viṣṇunā - by Lord Viṣṇu; hatam - was killed; mahā-asuram - a great demon; kālanemim - by the name Kālanemi; yadubhiḥ - with the members of the Yadu dynasty; saḥ - he (Kaṁsa); vyarudhyata - acted inimically.
Persons who are demons, enemies of the Supreme Personality of Godhead, are called asuras. As stated in Bhagavad-gītā, the asuras, because of their enmity toward the Supreme Personality of Godhead, take birth after birth in asura families and therefore glide down to the darkest hellish regions.