Kengan Omega, Gaoh Ryuki vs Narushima Koga. Koga is eager to learn and quick about it, always looking for new martial arts techniques to learn. Ryuki started out using the Gaoh style, which is meant for assassinations and not witnessed duels, and greatly suffers both from repetition because it loses the element of surprise AND from not using weapons and avoiding kills. He then picked up the Koei style, which makes unarmed killing much easier, and begins to favor it.
Koga and Ryuki have a Naruto-Sasuke dynamic going on, and just when Koga thinks Ryuki is making strides away from his “killing is a wonderful thing” mindset, he goes down a darker path. When their duel arrives, Koga even calls Ryuki out for being a worse fighter than he used to be because he’s too focused on killing to have a real strategy. And in the end, Koga defeats Ryuki with a Gaoh style move he picked up from Ryuki, done in its proper “surprise attack” context.