Sub-genre/trope of danmei (Chinese BL) where there's a scum gong (top) and an innocent/kind shou (bottom) couple. The scum gong is an asshole from the beginning of the relationship, usually also toxic, and then he really REALLY fucks up. The rest of the novel is dedicated to the scum gong trying to get back into the shou's good grace. There's a lot of regret and groveling and of course angst! The books can have happy or bad endings.
Similar to the rejected mate or second chance tropes.