01. "I Know What You Did Last Summer" and "Heaven and Hell" because they were wastes of time. The only good parts was the introduction of Alastair and Dean revealing what happened in Hell, that's it. Everything else is forgettable and, quite frankly, I pretend these episodes don't exist.
02. "Hammer of the Gods" because they killed Gabriel. ;__;
03. "Route 666" Racist truck? Seriously?
04. "Swan Song" since it is probably the worst finale in the history of this show. They totally over-hyped the finale saying that it was going to be amazing when, in reality, it was incredibly anticlimactic for a biblical apocalypse. The whole thing was such a mess and completely lame, I can't even. Never should have happened, or if anything should have been handled differently than what they did with it.
05. "Exile on Main Street" It just sucked and failed on bad on so many levels, just, no. That is not how you do a season opener. Just like the S5 finale, this season premiere was absolutely atrociously awful and perhaps one of the things that should have been a red flag for what this season was going to feature, and that ain't good. -__-
06. "Caged Heat" I think everyone knows why. Ewwwww. That episode never happened in canon, either.
07. Almost every episode this season so far, with the exceptions of the few I actually enjoyed. Also, filler episodes that could have been avoided altogether. I do like stand-alones, but fillers just for the sake of fillers are pointless and boring and amounts to nothing interesting.
As you can immediately tell, I am incredibly opinionated on this since in recent seasons there have been plenty of episodes that I wished never existed. Either from the writing (characterization especially) or direction of where storylines were headed, this show has been giving us some turd-worthy episodes lately and that concerns me greatly. I don't know if it's the direction and decisions underneath the new showrunner or what, but it's not going well at all. :/
Rest of the 30 Days of Supernatural Challenge.