My most hated anime had to be Fooley Cooley, honestly. It was just too misceláneo and just completely confused me. And it annoyed me so much... But who knows. I might give it another shot one day.
(I don't have any pics of that anime, so have a picture of my beautiful husband...I feel this one fits the mood)
oml, there's so many anime's I hated, and really crappy anime, I would say boku no pico, cause wtf is that shit, but then, I gotta admit, Fooly Cooly, it was everywhere, didn't at all amuse me and fuck sake, make a story line, and stay with it.