I taught elementary school for a couple of years after undergrad. Trust me, kids love stuff like that. Every child I ever taught loved the (Chinese) legend of Lon Po Po, in which the big sisters outsmarts and then brutally murders the wolf that was going to eat her and her baby sisters.

And there was this one particular book series that my kids followed, mostly for the settings/plots and partially because they were waiting for the main character's little sister to get herself brutally slain. (But they all agreed that the big brother was a great big brother for keeping her safe no matter how stupid she was.) I think the author was going for spunky, lovable, and plucky with the little sister. Clearly, she miscalculated.

Some of the most brutally efficient and completely chilling alternative endings to fairytales/novels that I've ever heard were proposed by my second, third, and fourth graders. And my fifth graders were bitterly disappointed that the Count of Monte Cristo didn't win in the end. (Okay, I was kind of an odd teacher in terms of my book selections. I can acknowledge that now. But my kids were totally into it.)