Let's see...so many to choose from....
Killing off Gwen Stacy. It helped pave the way for so many other pointless deaths and the women in refrigerators phenomenon.
Making Electra evil/insane. (No explanation needed.)
All that crap they did with Gambit's origins and making him a horseman of the Apocalypse. He was my favorite character! Why God Why?
The whole Spiderman clone story.
Cyclops deserting Jean for Emma Frost.
Gwen Stacy having Norman Osborne's illegitimate children.
Avengers Disassembled and Wanda's now being an insane super-villainess.
M-Day.
Spiderman; the Other.
Killing off Gwen Stacy. It helped pave the way for so many other pointless deaths and the women in refrigerators phenomenon.
Making Electra evil/insane. (No explanation needed.)
All that crap they did with Gambit's origins and making him a horseman of the Apocalypse. He was my favorite character! Why God Why?
The whole Spiderman clone story.
Cyclops deserting Jean for Emma Frost.
Gwen Stacy having Norman Osborne's illegitimate children.
Avengers Disassembled and Wanda's now being an insane super-villainess.
M-Day.
Spiderman; the Other.

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