Halloween 2.
Far worse zombie movie by far. ;) I've never wanted a main character to die so quickly. I think it took about 2 minutes in and I wanted Laurie to die horribly. That feeling never left either, but in fact it grew to an overwhelming passion throughout the movie. And yes, I actually liked the first Halloween by Rob.
Seriously though, how about
Dead & Deader? I made it about 10 minutes in and had to turn it off. I never noticed that it was Dean Cain when I grabbed it at the video store. I don't think I've seen a worse movie in my life.