I've seen a lot of manga with a very similar premise to this, but I like how here he's just totally willing to directly murder people for the sake of his goal. It's unique. Most of these manga will, at best, have the reincarnator be the scheming manipulative sort or "I beat you up, but I'll spare you and send you to jail instead."
Plus, having him kill people like that actually works out well in justifying why the "good guys" from the original story would still have a problem with her.