Omen Hell Axle, also referred to as Diamond Hell Axle, is a secret move used by Heihachi Mishima from Tekken 4 until Tekken 8, where it was removed. It acts as an enhanced version of Heihachi's Hell Axle. A noticeable difference between this move and the standard version is the blue sparks that erupt from Heihachi as he attacks. The overall attack also receives a damage boost.
In Tekken 4, this move was called Dragon Axle, as it could only be performed as a special combo after a delayed Dragon Uppercut. When the delayed variant of the Dragon Uppercut was removed in Tekken 5, the move was instead linked with the returning Supercharger instead.
In Tekken 7: Fated Retribution, the second kick, like the standard Hell Axle, will Screw the opponent.