Rukia
Kuchiki

Rukia Kuchiki starts the story by committing a capital crime: she gives her Shinigami powers to a human boy because a Hollow is about to kill his family. The series never lets either of them forget it. She spends the early episodes powerless, sleeping in Ichigo's closet, drawing terrible rabbit diagrams to explain Hollows, and quietly carrying the guilt of her lieutenant Kaien Shiba, who she was forced to run through with her own sword after a Hollow took his body.

When Soul Society comes to collect her, it sends the two people who matter most: Renji Abarai, who grew up with her in the Rukongai slums, and Byakuya Kuchiki, the brother who adopted her into the nobility and then barely spoke to her. She accepts the death sentence with something close to relief until Ichigo tears through the Seireitei to stop it. The execution arc ends with the reveal that the whole thing was scaffolding for Sousuke Aizen's theft of the Hogyoku, the orb Urahara had hidden inside her body.

She rebuilds herself from there. Her Zanpakuto, Sode no Shirayuki, is called the most beautiful ice blade in Soul Society, and in the Thousand-Year Blood War she shows what it actually does: it drops her own body temperature toward absolute zero, freezing whatever she touches. Against As Nodt, the Sternritter whose fear magic broke Byakuya, she reveals her Bankai, Hakka no Togame, and shatters him frozen. By the Wahrwelt invasion she is lieutenant of the 13th Division, marching on the Quincy stronghold beside the captains.