Balarama immediately struck the demon's (Pralambasura's) head with His strong fist, and the demon fell down dead as if he were a snake whose head had been smashed
“"When Kṛṣṇa was defeated by Śrīdāmā, He had to carry him on His shoulders. Similarly, Bhadrasena carried Vṛṣabha, and Pralamba carried Balarāma, the son of Rohiṇī."
This verse is from Śrīmad-Bhāgavatam (10.18.24). When all the cowherd boys were playing in the forest of Vṛndāvana, the demon Pralambāsura appeared in order to kidnap Kṛṣṇa and Balarāma. The asura appeared disguised in the form of a cowherd boy, but Kṛṣṇa could understand his trick. Kṛṣṇa therefore divided all the cowherd boys into two parties. One party belonged to Balarāma, and the other party belonged to Kṛṣṇa Himself. Ultimately Kṛṣṇa was defeated in this play, and according to the wager, the defeated party had to carry the victorious party on their shoulders. Kṛṣṇa had to carry Śrīdāmā on His shoulders, and Bhadrasena had to carry Vṛṣabha. The demon Pralambāsura had to carry Balarāma, and when Balarāma mounted his shoulders, the demon ran far away. Finally the demon began to expand his body to a gigantic size, and Balarāma understood that he intended to kill Him. Balarāma immediately struck the demon's head with His strong fist, and the demon fell down dead as if he were a snake whose head had been smashed.