Soukou no Strain
I'm not 100% sure it's
hated per se, but it does seem to be overlooked and forgotten. It's not really the best series in the world, but I like it just the same. Bonus points for having an absolutely awesome first-episode Wham Episode.
El Cazador de la Bruja
Yeah I know practically everyone hated this. It was really weird, way weirder than either of its predecessors, but being a yuri fangirl I squee'd pretty hard over Nadie and Ellis. Plus the villain made me giggle, and the Mexican cross-dressing bounty hunters were hilarious.
Umineko no Naku Koro ni
I realize that most of the people who hate this series are those who have read the VNs, but still, I think the hate is unwarranted. Umineko marks the first time I've really seen Studio DEEN not totally go Off Model every five seconds (ugh, DEEN, I love
Shion no Ou but wow you guys really screwed it up half the time) and I find the show itself to be entertaining.
No, I haven't read the VNs and I don't plan on doing so.