SB 3.3.1
uddhava uvaca
tatah sa agatya puram sva-pitros
cikirsaya sam baladeva-samyutah
nipatya tungad ripu-yutha-natham
hatam vyakarsad vyasum ojasorvyam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Sri Uddhava said: Thereafter Lord Krsna went to Mathura City with Sri Baladeva, and to please Their parents They dragged Kamsa, the leader of public enemies, down from his throne and killed him, pulling him along the ground with great strength.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
King Kamsa’s death is only briefly described here because such pastimes are vividly and elaborately described in the Tenth Canto. The Lord proved to be a worthy son of His parents even at the age of sixteen years. Both brothers, Lord Krsna and Lord Baladeva, went to Mathura from Vrndavana and killed Their maternal uncle, who had given so much trouble to Their parents, Vasudeva and Devaki. Kamsa was a great giant, and Vasudeva and Devaki never thought that Krsna and Balarama (Baladeva) would be able to kill such a great and strong enemy. When the two brothers attacked Kamsa on the throne, Their parents feared that now Kamsa would finally get the opportunity to kill their sons, whom they had hidden for so long in the house of Nanda Maharaja. The parents of the Lord, due to parental affection, felt extreme danger, and they almost fainted. Just to convince them that They had actually killed Kamsa, Krsna and Baladeva pulled Kamsa’s dead body along the ground to encourage them.