Kishin Hunter (Kishingari, anime version) is a Soul Resonance technique in the Witch Hunt series of scythe resonance attacks. It is present within the Soul Eater anime and in chapter 111 of the Soul Eater manga. It is possibly the most powerful form a scythe-weapon can assume.
It is unknown what the attack's capabilities are, but it can be assumed it is effective in killing immortals like Kishin Asura. Asura does mention it as being another move intended to erase evil, similar to Majin Hunt in that regard, possibly making it a more powerful version of Majin Hunt.
In the anime, Shinigami was the frst one to use it and managed to use it to completely sever one of his arms. Later, in the last episode, Maka was able to use it to cut into Asura's torso, but it still proved ineffective in killing him, as he shattered the technique and healed his injuries quickly after. Like Majin Hunt for Maka, the attack carries her Anti-Demon Wavelength though Asura claimed it didn't kill him because he is the embodiment of madness and madness itself not inherently evil or impure as everyone has it.
This is different in the manga, as Kishin Hunt is ultimately what Maka uses to aid Crona in sealing Asura away.
In the manga, the Kishin Hunt works slightly differently than in the anime. Maka activates the ability as she attacks Asura with Soul in his new scythe form after they control the black blood. It allows her to enter the Kishin and find Crona. As she exits Asura she completes the Kishin Hunt attack, attacking Asura as she leaves and fatally injuring him. This makes him bleed and allows Crona to use the Mad Blood ability to seal him once and for all.
In both the anime and manga, Maka is not able to use this technique until the last episode/last volume while fighting Asura, likely to demonstrate how much her skills had developed by the end.