Disappointing game endings [SPOILER FILLED THREAD]

[Sirion]

Have you ever played a game from start to finish, completing each side quests/missions, paying full attention to every dialogue and scenario details to make sure you don't miss anything about the story... just to find out it all messes up in the end?

My deception came from Prince of Persia: The Two Thrones.
[spoiler] After killing the Vizier, Prince is thrown into his own mind by the Dark Prince, where he must play some kind of dumb puzzle game and fight Dark Prince now and then. It would be ok if Dark Prince didn't end up to be an attention whore douchebag that can't add an inch of deepness to Prince's character, or his own's. All this double personality thing had so much potential, only to be wasted, making Dark Prince nothing interesting but a new gameplay feature.[/spoiler]


So, tell me your deceptions. *Brace yourselves, Mass Effect 3 rants are coming*