In the Bleach anime, many diverse characters are introduced in an ever-expanding cast, with nearly all of them getting a compelling backstory at some point. Early on, Ichigo's tragic backstory involving his mother Masaki was fleshed out, and then Rukia Kuchiki got her turn. But what about Kenpachi Zaraki, the thuggish Captain of Squad 11?
At first, Kenpachi seemed like the typical berserker type, but there's more to him than scary looks and bloodthirst. Kenpachi had a tough childhood and experienced more than a few life-changing moments, with more twists laying ahead in his personal arc. These five events defined his character arc the most.
The First Time Kenpachi Fought Yachiru Unohana
Kenpachi did not have an easy childhood. He was born in the 80th and poorest region of the Rukongai District, a place rife with crime and violence, and the boy came across a dead Soul Reaper's generic Zanpakuto. Kenpachi claimed it and imprinted his soul onto it, then faced Captain Yachiru Unohana of Squad 11 in mortal combat. Despite his youth and lack of experience, Kenpachi put up a good fight, ultimately losing because he purposely held back.
This clash established Kenpachi as a bloodthirsty but sporting warrior, and Yachiru Unohana (later going by Retsu) expected good things from him. His warrior career had begun, and he longed to train hard to surpass the mighty woman who defeated him in a street fight. She became Kenpachi's first role model.
When Kenpachi Met Yachiru Kusajishi
Despite being a rough young man, Kenpachi was not a total monster. He had a sense of honor and sportsmanship, much like the Arrancar named Grimmjow Jaegerjaquez, and he even made a friend. Years after fighting Yachiru Unohana, Kenpachi came across a young girl who had zero fear of him and his Zanpakuto and unofficially adopted her. He named the child Yachiru, after the Soul Reaper he'd fought, and gave her the last name Kusajishi.
Kenpachi soon became highly protective of her, even if he won't admit it, and this established his lovely tsundere side. Little Yachiru became Kenpachi's Lieutenant in Squad 11 years later, and defending her would help spur him to new heights while fighting foes such as Nnoitora Gilga and Gremmy Thoumeaux.
When Kenpachi Lost To Ichigo
During Bleach's Soul Society arc, Ichigo and friends faced many powerful Soul Reapers. Ichigo first faced Ikkaku Madarame and Renji Abarai, then Captain Kenpachi Zaraki himself. Kenpachi had a huge advantage in strength and experience, but he and his nameless Zanpakuto were not in sync. By contrast, Ichigo and his own Zanpakuto, Zangetsu, became a tightly-knit team and overwhelmed Kenpachi with their united powers.
Kenpachi was humiliated, but it did prompt him to try once again to learn his Zanpakuto's name and actually listen to it, rather than use it as a blunt instrument of battle. This defeat also shook Kenpachi out of his complacency, which probably helped him narrowly win against the mighty 5th Espada, Nnoitora Gilga.
When Kenpachi Killed Yachiru Unohana
In the Thousand-Year Blood War arc, Kenpachi was designated as one of the "five war powers" in the eyes of the Sternritter -- despite that, he had not yet realized his potential. He once again crossed swords in mortal combat with his old nemesis, Captain Unohana. Yachiru summoned all her bloodthirst and delivered a serious beating on her protege, even using her Bankai, Minazuki, for added effect.
However, Kenpachi had learned much by now and finally turned the tables, killing Yachiru. This act brought him no joy. He had just lost his greatest role model and rival, but his grief helped harden his resolve and learn enough humility to unlock his true potential at last. He had finally stepped out of Yachiru's shadow, and greatness awaited him.
When Kenpachi Awakened His Shikai, Nozarashi
Bleach featured many dramatic Shikai and Bankai reveals, but few were as exciting as Kenpachi's. During the fight against Sternritter "V" Gremmy Thoumeaux, Kenpachi finally showcased his Shikai, Nozarashi, proving at last that he was becoming a proper Soul Reaper. Not even someone as powerful as Kenpachi could fight alone forever, and after slaying Yachiru Unohana, he heard his Zanpakuto's voice for the first time.
Kenpachi had become stronger than ever, using this astonishing power to defeat Gremmy in spectacular fashion. After that, there was no going back.