Wardance...?

Requires owning Yanqing. Yanqing can be found in the Forgotten Hall Xianzhou Stage 2.

Wardance: This term often refers to a dance performed either before going into battle or during a battle, intended to intimidate the enemy and boost the morale of one's own troops. There is a series of achievements named "Wardance: [weapon] Trial" in which you have to defeat Yanqing with various different characters. This achievement requires you to defeat Yanqing with Yanqing, so instead of a weapon name it suggests confusion at the fact he is apparently defeating himself.