Hienzan

Hienzan (Flying Swallow Slash) is one of Kim Kaphwan's signature Special Moves throughout both the Fatal Fury & King of Fighters series, first appearing in Fatal Fury 2.

Description
The user does a backflip kick with their rear leg.

In the case of Kim Kaphwan, Chae Lim & Gang-il, thye can follow up with Tenshouzan (Sky Rise Slash) - occasionally called Oi Uchi (Chasing Attack), where they kick the opponent back down with a hammer kick.

Jae Hoon's version powered up with flames.

Chang's version - known as Tekkyuu Hienzan (Iron Ball Flying Swallow Slash) - possibly due to his weight, he fumbles the kick and lands on his back before making a full rotation.

Strategy
To be added soon...

Trivia

 * Choi's version of the attack is written as a homophone - ; Grieving Monkey.