Ultimate Spider-Man #13: Hobgoblin
by Brian Michael Bendis & others
The good news: Harry Osborn is back! The bad news: he's been brainwashed and turns into a fiery hobgoblin who wants desperately to kill Spider-Man. Also bad news: Peter is failing at keeping MJ safe so he has to do the only thing he can think of: break up with her.
Boy, this arc sucked plot-wise. All the comics were great, but it tore my heart out and stomped on it repeatedly. Oh Harry. Sucks to be manipulated like that! Oh MJ, you're totally still in love with him and he doesn't want you hurt. Oh Peter, you seriously cannot catch a break, can you?