Hell Knight is the 134th episode of the Katekyo Hitman Reborn! anime.
Genkishi recalls a certain memory of when he had been ordered by Byakuran to annihilate the Giglio Nero Family, but was too intimidated by Uni's eyes to do so. Genkishi tries to gain even more power from the ring in order to make up for his blunder and transforms into a skeletal figure. However, Tsuna sees through his scheming plots and prepares to fire a full powered X-Burner.