The Anime Lad
A boy bullies the deaf girl in his class until she transfers away, and the class makes him the scapegoat for it. Years later, isolated and ashamed, he studies sign language and goes to find her. Nothing about the redemption comes easy or cheap. The animation is gentle with material that isn't. It treats every character like a person, including the ones who don't deserve it.
Gigguku
The gentlest-looking film in the room, pointed at material most directors would flinch from, and it never flinches once. I've recommended it to more people than any other film, with the same warning every time, it will hollow you out for a day or two, and you'll be glad. The bully is the protagonist and the film makes that work without excusing him for a second. It's about earning your way back to people. Worth it every time.
Father's Basement
Bully-seeks-redemption is usually a machine for cheap tears, so I had my arms crossed from the opening frame. This one makes everybody pay full price. The victim isn't a saint, the bully isn't secretly misunderstood, the class that enabled everything gets no free pass, and forgiveness costs everyone something real. It handles disability and guilt with a seriousness most live-action dramas can't manage. I uncrossed my arms somewhere in the first act and never got them back.