What was the saddest death you have ever seen in any Marvel comic? Mine's were:
Colossus' death in "Legacy Virus arc" Colossus sacrificing his life during the Legacy Virus arc was so sad because he was willing to give up his life to save all the people he loved.
Jean Grey's death in "The Dark Phoenix Saga:" It was so sad because of the fact that Jean Grey sacrificed her life to save the world from her dark phoenix persona.
Nightcrawler's Death in "Second Coming:" Nightcrawler dying is always sad since he's such a lovable character. His death still affects everyone to this very day.