The Good Wife series finale - The creators have admitted that they planned out Alicia getting slapped by someone as the final scene... ever since the first season. They clearly reverse-engineered this finale just for that one moment, coming up with plot points that made no sense and giving us an ending that made the main character look awful. We'd really hoped for better from such a smart, amazing show.
Grace: But Dad, you have to fight this. Peter: I can't risk being away from you until you're thirty. Grace: But it's two years. Peter: I'm going to be at your graduation in the front row.