2. Spider-Man
The Plot: Peter Parker is bitten by a radioactive spider. Fun and joy ensues--if by fun and joy, I really mean emotional trauma. Peter's uncle dies tragically, and it's all his fault, so he decides to become a hero. Meanwhile, Peter's mentor, Norman Osborn, accidentally turns himself into the Green Goblin, who goes out to kill all of Osborn's business competitors. And he succeeds, but then goes after Spider-Man.
The Solution: Just stop while you're ahead. Green Goblin won. Why does he care about Spider-Man? He never expresses any real motivation to kill him beyond "AH! SPIDER-MAN! BREAK THE SPIDER!" He has no motivation, no reasoning behind it, so why do it? Norman will be completely unaffected by this, so why even bother? Oh, and if you think that's bad, consider this: if the Green Goblin stopped, then Norman wouldn't threaten Mary Jane, and Peter wouldn't have ended up "killing" him, so Peter would have no motivation not to be with Mary Jane, and Harry would never vow vengeance on Spider-Man. That literally resolves an entire half of the film trilogy's convoluted plot. Think about it.