SB 6.12.32
bhittva vajrena tat-kuksim
niskramya bala-bhid vibhuh
uccakarta sirah satror
giri-srngam ivaujasa
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
With his thunderbolt, King Indra, who was also extremely powerful, pierced through Vrtrasura’s abdomen and came out. Indra, the killer of the demon Bala, then immediately cut off Vrtrasura’s head, which was as high as the peak of a mountain.