This arc is building up to... the author's perspective on forgiveness told through his characters. While I can totally understand some people will dislike it because it defies the pattern built so far, I can also appreciate the subversion, because from what I see the spirit is still there: the would-be victim is left alive not because she's forgiven, but to make her suffer more.
Also because I practically read the arc in one go, so there's one more reason why I can enjoy it more. I don't have to wait for each build-up chapters.