Kenpachi Zaraki vs. Retsu Unohana

Retsu Unohana vs. Kenpachi Zaraki is a fight during the Quincy Blood War between the 11th Division Captain Kenpachi Zaraki and the 4th Division Captain, Retsu Unohana. The expressed purpose being to help Zaraki to become more powerful by finally teaching him the art of killing.

Prologue
After announcing his decision to the Central 46 of wanting to have two lieutenants, Shunsui Kyōraku goes on to reveal his intention of having Retsu Unohana teach the 11th Division's Captain, Kenpachi Zaraki, how to fight. Giving them permission to use the prison's lowest level, Muken, as a stage for their training, the two captains descend and find themselves in an infinitely wide, featureless floor. Exchanging words, both former and current Kenpachi draw their weapons in preparation before lunging at one another.

Battle
Beginning their battle, Unohana quickly gains the upper-hand by landing several direct hits on Kenpachi, leaving the latter quite bloodied while the former manages to stay unharmed. Lunging at her with a downward strike, Unohana redirects his blow with her spare, left hand and cuts the man's throat open with her own blade. Jumping back a little, Kenpachi tries again to swing at his opponent, only for her to step onto his wrist while preparing her own downward strike. Seeing this, Kenpachi is quick to flip over and kick her in the ribs, sending her towards a nearby rock wall, to which Unohana is able to recover from his blow and use the rock as a launching platform for their next powerful clash, a shock-wave emanating from their Zanpakutō colliding.

Praising Kenpachi for being smart enough to remove his eye-patch at the very beginning, Unohana also points out that it means he's already fighting at full strength. Impaling his left shoulder with a hidden knife, Unohana tries to cut Kenpachi while he's distracted, only for the latter to parry her blow. Moving back to get some distance between them, Unohana calls him out on his lazy fighting-style, claiming that people who fight with only one hand on their sword while the other does nothing cannot possibly enjoy the fight. Countering by calling her trick with the knife as pathetic, Kenpachi declares that she was no longer the woman he used to respect.

Angered by his admission of respect, Unohana quickly moves against Kenpachi, disarming him and pinning the man against a rock wall, the point of her blade to his throat. Explaining that she hadn't used her knives before because Kenpachi hadn't let her do so in the past, Kenpachi is left asking if he's grown weaker. Reminiscing about his past, the man recalls how nothing he had cut or fought had given him a thrill until meeting her. Shedding a tear, Kenpachi asks if he was about to die a miserable death without ever having defeated her. Giving no answer, Unohana simply impales him straight through with her Zanpakutō and looks on as the man began to lose conciousness.

Moments later, Kenpachi is surprised to find himself regaining his senses and feeling more alive then ever, with his sword in hand again and blocking Unohana's blade. Wondering what had just happened for a second, the man quickly dismisses it from his mind and focusses entirely on the battle at hand. Meanwhile, Unohana is left to her thoughts, admitting to herself that Kenpachi won't be the one to die as he grows stronger every time he nears death.

As the fight goes on, Kenpachi quickly realises that he is continuing to black out only to regain consciousness moments later. Waking up while airborne, the man reaches out to the ground with one hand to slow his momentum before regaining his feet and attacking once more. Disturbed by the fact he's constantly losing conciousness despite never having done so before, Kenpachi remembers that there had been one time he had passed out, and that it was when they had fought previously. Also recalling their first ever battle, Unohana acknowledges that Kenpachi was the stronger, and that it was during this time he had subconsciously placed limitations on his power from the fear of killing those who he could enjoy fighting.

Blacking out yet again, Kenpachi wakes up in time to avoid Unohana's attack and counters with his own, finally landing a blow on the woman. Noticing he was able to react to her attacks on reflex rather then having to concentrate like before, he realises that every time he regains conciousness he feels as though he is being reborn. Continuing to rain lethal blows on him however, Unohana admits her aim wasn't to defeat the man, but to help him unlock the power he once possessed. Healing him every time he was about to die, Kenpachi became closer and closer to achieving that level of strength, until finally came the moment where he lands a devastating blow on Unohana.