Transformers was easily the worst of this year that I've seen. It was just painful to watch.
Lucy was pretty bad, Godzilla was poor, as was Amazing Spider-Man 2, but all were at least watchable. TF4 was the only one where I wanted to walk out - I would have, but I watched it to pass some time as I was stuck in town for a few hours.
I also hated Neighbors, but that was more just that it's not my thing. It wasn't a bad movie per se, I just don't like "dick jokes", that sort of 'comedy'.
Those are the only bad ones I've seen this year. I expected Dracula Untold to be god-awful, I just watched it because I was with friends and nothing else was on, but it was surprisingly good.