The X-Men have gotten a reputation for dark stories over the years. Comics like The Dark Phoenix Saga and Days of Future Past threw brutal endings at readers, but honestly they mostly made sense for the stories they were in. X-Men stories since those two have often gone in pretty dark directions, but most of the time it made perfect sense because they were built up to be dark stories. That's not the case with all of them, though.
Source：https://www.cbr.com/xmen-best-comics-surprise-dark-endings-ranked/
