When a school child is killed in a botched kidnapping case, a young superhero decides to retire, but her long-lost nemesis reappears–an evil superhero who also happens to be her brother.

Just wanna say first that are my reactions and other people’s mileage may vary. Just saying “child” would grab me more than “school child.” The causality of the botched case to the retirement is there, but could be stronger and make it so I didn’t have to work for it (I’m a lazy reader). I think what is missing is a word or two about the emotional impact on the superhero. “When a school child is killed in a botched kidnapping attempt (rather than case, case makes if feel more like a job she was working, not a calling), a young superhero blames herself and retires. Or something like that, because I think you need an emotional hook relating to the protagonist. Next nit: isn’t an evil superhero a supervillain? Also phraseology of “who happens to be her brother” is weak (don’t like “happens”). Prefer something like “…but a long-lost supervillain and arch nemesis reappears–her brother. My last comment is that while I’m interested in a family dynamic with superhero sis/supervillain bro, this leaves me hanging. I can invent all manner of difficulties this might promote but prefer that you direct my understanding of the ramifications. It implies, but does not state, that the reappearance will lure her out of retirement. It doesn’t say what the actual obstacle is, what is the brother doing and what will she do about it (in very general terms). Like he’s the one behind the kidnapping/planning another and she puts on her superhero boots again to bring him to justice/prevent him. Or whatever is the situational obstacle and what she is doing about it (and a bonus for how she feels about what she has to do utilizing a word or three like I did when I said she blamed herself). Hope this helps. Good luck