Kill count in one battle

whereupon Arthur, provoked to see the little advantage he had yet gained, and that victory still continued in suspense, drew out his Caliburn, and, calling upon the name of the blessed Virgin, rushed forward with great fury into the thickest of the enemy's ranks; of whom (such was the merit of his prayers) not one escaped alive that felt the fury of his sword; neither did he give over the fury of his assault until he had, with his Caliburn alone, killed four hundred and seventy men. The Britons, seeing this, followed their leader in great multitudes, and made slaughter on all sides; so that Colgrin, and Baldulph his brother, and many thousands more, fell before them. But Cheldric, in this imminent danger of his men, betook himself to flight.

History of the Kings of Britain