Honestly this is going to be a short list. If there is an anime I don't like, generally I don't waste my time finishing it. So with the parameter of least favorite, having actually finished, well there isn't much.
Series:Neon Genesis Evangelion -to be fair, I watched this pretty early on, before it got overly hyped. The robot designs and anime style are pretty good, but the story is absolutely atrocious. I know you need conflict and drama to make a decent story, but the fact that the protagonist is a miserable little puke, and everyone else around him is more awful than he is, just makes me depressed. No thanks. Also the fact that this series is often at the top of anime lists in terms of Mech/Super Robot series just makes me ill. There are so many better Super Robot Series out there.
Tengen Toppa Gurren Lagann -this one, unfortunately I watched based solely on all the hype generated around it. I should have known better. I watched it on Netflix. I really tried to like it, but couldn't. The ideas I guess just had too much over-the-top silliness to me, The series was all over the place. Was it serious? Was it comedy? Was it fan service? I have no idea. The idea of a robots that increased in size/power over time based on gaining new additions was novel, but then when the final form is bigger than the entire galaxy, or whatever it was, sorry you lost me there. I know fantasy is about breaking boundaries, but I'm sorry even in the fantastical world of Super Robots where laws of physics and logic typically don't apply, there has to be some sense of scale. It just seemed like the kid on the playground who said his toy has infinite god-like powers, and destroys your toy. You don't want to play with that kid anymore. Looks like he just got his own anime, and yeah, I'd rather not watch it.
FilmsProject A-ko Ah memories. Can't believe its been 25 years now. But back in 1991 I was in highschool. Blockbuster Video started having this thing called "Anime" (which looked a lot like Star Blazers, Voltron & Robotech, stuff I had grown up with). So yeah... it must all be good right? - Wrong! -Project A-ko taught me that not all Anime is Good Anime, and I would have to be more selective in the future.
Dominion Tank Police-Apparently a couple years later I still had not learned my lesson. The Sci-Fi Channel in the early 90's showed 3 great anime classics (Vampire Hunter D, Robot Carnival & Lensman). However the next year they started showing more and DTP was one I recorded because- if it's on sci-fi it has to be good right--again I was wrong, and I learned my lesson. I wonder what ever happened to that old VHS
Probably long gone.
Roujin Z -Now this is odd. This isn't so much a least favorite as much as -I have no recollection of it. I know I watched (perhaps even recorded it) off Sci-Fi, but for the life of me I have no idea what it is about. Kind of sad I cant even remember something I watched.
There are no more good TV Shows, only ones that haven't disappointed me yet.