The Dark Phoenix Saga
Spoilers ahead, maybe
I am no fan of Jean Grey.
I mean, it's a character with potential, I suppose. Jean Grey and Phoenix both. A telekine and weak telepath, with vast reserves of power which, when tapped, slowly take her over. There are things you can do with that. Cool things. Megalomania is an entertaining plot device when handled properly.
However, over the years, the writers who have taken on the story of Jean Grey and Phoenix have gone far past proper handling and into the realm of death, shark-jumping and general headachey terror. The original Dark Phoenix Saga is a fantastic story with a lot of impact. It's a story about someone learning self-control, and ultimately also about a superhero committing suicide. And that's intense, and the sort of thing that people sometimes have difficulty dealing with.
But really. I wish she'd stayed dead.
...I know. Comic Book Death. Nobody stays dead except Barry Allen, and even that might be in doubt. But there's a difference between dying and coming back once, and dying and coming back every few years. Like I said, it's a character with potential. It's a compelling idea. But it's overdone. Hey, Grant Morrison did some cool Dark Phoenix stuff in New X-Men, which I love like crazy, and I still found it tiring.
Also, I don't like characters whose primary purpose seems to be rescuing writers who have written themselves into corners. Wolverine's dead? Whoo! Phoenix saves the day! World ending as you ride a meteor into the sun? Phoenix! Sublime is destroying all of civilization in a horrifying alternate future? Phoenix!
Godsdamn, people. Phoenix is not the answer to all your problems. In fact, at this point, she's not really the answer to any of them.
Please stop. For the Professor's sake.