First, I know that there is a Bully Hunter
trope, but I think
this could be different since it involves rescuing a specific person who is the target of abuse and doesn't necessarily involve a general crusade against bullying.
The way this generally plays out is that character A who is physically weak and often fat is being picked on and character B, the hero rescues them. Character A will be extremely grateful and will be the hero's loyal supporter thereafter.
However, it's possible that character A is the hero, in which case character B is the Big Brother Mentor
- One of the earliest examples is probably Tom Brown's Schooldays which is like the ur-example of the "school story" genre. First, I believe to a degree, this plays out with Scud East protecting Tom (the hero) from Flashman, but the more trope-worthy example is an older Tom protecting George Arthur, who is physically weak and a sensitive intellectual.
- Given a deconstruction or possibly Unbuilt Trope in Vanity Fair. Dobbin rescues George from bullies at school, but in the past, George had bullied Dobbin himself and while this incident makes the two friends, George is a spoiled jerkass and as the two grow into adults, George tends to take advantage of Dobbin and Dobbin ineffectually tries to appeal to George's better nature.
- In A Song of Ice and Fire, Jon Snow rescues Samwell Tarly, who is fat and a self-proclaimed coward, from bullying and sadistic treatment by the trainer at the Wall, and the two become friends. Samwell is a POV character who is really more like The So-Called Coward and even though he's not really a warrior, he manages to accomplish a lot through his intelligence.
- The Harry Potter series borrows a lot from the school story genre, and this tends to play out with Harry and friends protecting Neville Longbottom from Malfoy and co. However, Neville ends up Taking A Level In Badass by the end and even has Memetic Badass status.
- Interesting subversion in the manga Alive: The Final Evolution. Taisuke the hero is kind of a Bully Hunter and befriended the physically weak Hirose after rescuing him from bullies. Hirose initially ends up Brainwashed and Crazy, but then gets freed from that and becomes a cunning Omnicidal Maniac. In part, this change was due to his resenting Hirose, as needing to be protected underscored his feeling of weakness.