Destroy All Living Beings with One Sword

[Single female protagonist + fast-paced gathering + decisive killing] Thousands of years ago, there was a shocking battle, and masters from all races fell together. What is going on here? Thousands of years later, a genius boy will be born. He will be trapped in a troubled world. So, what will be the fate waiting for him? Ask the boundless earth, who is responsible for the ups and downs? Only one sword!