Now I don't get that at all, because for me one of the main draws of fiction, and genre fiction in particular, is that it is escapist and less depressing than reality, so I pretty much only like genres that for the most part abide by the convention to deliver a happy ending, i.e. I like fanfic, romance, YA, mysteries, and the kind of SF&F where heroes win, and am much less into e.g. horror or "literary" fiction or other genres where that isn't the convention. Even when I read stuff like apocafic or such, I ultimately want it to end hopeful for at least the main characters.
So I don't really have any recs for media (books, movies or tv series) that end badly for the heroes overall, because even when I encounter the situation of just some of them not making it (like in HP) I'm on the look out for fix-it fic. But I wondered whether others might have recs that I could pass on to my niece to satisfy her odd (to me) preference for some variety and a more fraught fictional experience.
Though I'm not sure whether she wants depressing stuff or more things along the line of the fanfic type revisionist AUs with perspective shifts, because she mentioned that she was kind of rooting for Loki and Tom Riddle and such, i.e. where the story just takes the bad guys' side and for them it is okay, even though the world is then in the hands of a megalomaniac. I mostly dislike that type of fanfic as well. And I don't look for that kind of "twist" in original fiction either.
It would have to be stuff that is available in German and at least somewhat suitable for an eight year old.