Marvel has published a lot of stories with "shocking" twists. While some stories are written with the upcoming retcon in mind, such as Peter Parker revealing his identity in Civil War, other stories are written for the sake of story, killing off major characters, changing major characters, leaving Marvel to do an about face some years later.
What I am asking is - are there any stories that shocked you, thinking "wow" I cannot believe Marvel made this commitment to story. Stories they published which, at the time, had no intention of retconning.
My examples:
Killing Gwen Stacy
Killing Green Goblin
Killing Magneto in Morrison's run.
Aunt May Finally dying.
Hank Pym abusing the Wasp
Death of Kraven
I'm more of a Spider-Man/Daredevil guy. Wondering what other instances you can think of company wide.