Dexter - Season 6 finale. It went something like that anyways. In any case, quit after that. It's a shame it took me so long to drop because the show was shit a long, long, long ways from that episode and season.
Weeds - 7th season finale. Another shame in taking so much time to drop this one, as Weeds was a shitty show from the get-go. Whatever novelty it had wore off within season 1 and yet I kept watching for whatever reason. I finally decided to leave for good after that finale though.
Orange is the New Black - Season 1 finale. At least I learned my lesson from Weeds this time: Jenji Kohan. Never again.
Legend of Korra Season 1: An awful finale with a huge drop in quality due to poor pacing from a flawed concept. I was actually wise enough to drop this one after the first season.
The Walking Dead is another mistake within these halls still in progress. It has always been a bad show and the latest season was simply drop-down-dead boring. However, I'm still there to see how much it can shit the bed in poor characterization, drama and CG blood.