Okay, I am positive there are other shows that are the worst but I don't watch every channel so of the shows I HAVE watched...
Any "reality show". They are just horrible and showcase the worst types of people and behaviors. Not just the Bachelorette, all the dance/singing shows, or stupid MTV shows where drunken people with psychological issues share a house but also things like Toddlers in Tiaras (so so so so terrible) and a few other shows on TLC. I admit to watching some of the TLC shows, but its more like a train-wreck (I just can't look away but I know I should!).
Of the shows already mentioned - I agree with...
Glee. I liked it at first, but it has since fallen so short of the original potential. They did nothing of importance with the character who was texting while driving... it made me so mad and I was already hating on the show before that (that was just the last straw).
Are you there, Chelsea was also pretty bad. Not the worst, but I changed the channel more than once.
Revenge. I gave it a try, but it's just a night-time soap opera. My coworker (an older man) loves it, but it's just BAD.
2 Broke Girls & Whitney - agree for the same reasons. I kept giving Whitney a chance, and it was not as bad as 2 Broke Girls but still not something I cared about.