In the world of Eastern Animation, the good stuff is pretty easy to find. Brands like Dragonball (Classic, Z, and GT; not Kai), One Piece (subbed or Funimation, not the 4Kids crap) and Full Metal Alchemist (both incarnations, even as far off the rails as the original anime went relative to the original manga; even the English dub is good, I mean, they did bring the original dub crew from the first incarnation back for the second, that's gotta count for something) come to mind. But for every awesome episode of G.I.T.S. Stand Alone Complex, there's 2 unwatchable vomit piles of Death Note. Seriously, Death Note is the worst thing to come out of Japan since the Zero (and if you don't know what that is, go to your local VFW and ask the oldest person there). Watching a loop of Goku coughing up blood for 20 minutes is infinitely more fun than watching 5 minutes of Death Note, and I dare you to prove me otherwise! Let me get to the point: I want you to tell me what your least favorite anime series is, why you hate it, and (entirely optional) what you would have done differently with the story, characters, etc.

I'll tell you mine, as an example: Blue Dragon. I hate it with every fiber of my being, for three reasons. One, it doesn't even fit in the original game franchise's canon, which it should have been able to do, as it was supposedly based off the original videogame. Two, Akira Toriyama didn't have anything to do with it, regardless of his influences on the animation style. Although, that may have been a blessing in disguise because, three, the good guys are a bunch of tools. I can forgive the first two flaws, but the third, I'm afraid to say, I cannot. Let me tick them off for you: Hsu is likable enough, but we had to endure him stumbling out of the gate with his mystic shadow, the titular Blue Dragon, for the first four episodes; it's honestly too much to take. Cluck is a sweet girl, but for most of the series, she has no powers, and when she does get her own shadow, she overexpends herself and ends up in a coma. Zola is an icy bitch, and her traveling companion is too stuck on revenge for anyone to trust him. That Mero-Mero guy is good comic relief... for five minutes into the first episode he appears in. He's basically the most predictable kind of womanizer, who won't touch Zola because, again, she's an icy bitch. Then there's the accident-prone bimbo who rounds out the team later on. She's essentially as useless in combat as Cluck, but hey, she first appears with her shadow in tow, so that makes up for it, right? WRONG! As for what I'd do differently, I wouldn't keep Hsu green for as long, I would soften the demeanor of Zola and her traveling companion, I would give the comic relief better lines, I would not take more episodes than the original Tenchi Muyo! to bring the cast together, and I would save character development for AFTER the heroes assembled.

You don't have to be as long winded as I was, just say what you want, within the guidelines of this site and the confines of this topic.

Evangelion.

Kennyheart, get the fuck outta here... You hate Evangelion, and won't even state any reasons why? NOT COOL!

Lol, I would say.... Nabari no ou-> simply just the worst ending ever...

Tenchi in Tokyo.

I consider Tenchi Universe only slightly inferior or approzimately equal to Tenchi Muyo (I love em both), but I could barely stand watching Tokyo. It was almost morbid curiosity that got me through it. Every character without exception that I recall (though there might have been one or two) is a Flanderized or debased version of themselves. Ryo-ohki was especially irritating because of the stupid robot form. Barely any characters that used to be related to each other are anymore, presumably because the writers couldn't be bothered to spend the time on characterization. The technology makes less sense. Even the animation irritated me.

The traditional reason for Tenchi fans to hate Tokyo, Sakuya, wasn't even in my top three.

It's been over five years since I watched it, but the thing that still sticks out in my memory as singularly annoying was in the finale, where (it seems to my possibly-exaggerated memory) Tenchi spent half an episode running up the stairs to the final battle, running with that stupid giant crystal sword poised like he's about to swing it in five seconds, not five hours.

Yeah I thought Sakuya was way too over-dramatic. And then there's the terrible, terrible plot twist associated with her: [/spoiler_alert] she isn't even real! [/end_spoiler]

This is a bit of a tough one for me.  I don't think I have watched an anime that I haven't enjoyed (5 min worth at least).  And I know I don't own any anime that I don't like. 

But, I will do my best to give an answer and it is actually three answers.

1.  A series with too many damn episodes.  I want to own my anime and I don't have a shit ton of money so when something comes along that's over 9000 episodes long, I get iritated and usually can't give it the time of day.  Dragonball is excluded from this rant as it was something that I watched as a kid and still enjoy (Sunday mornings on WB11, 1 episode a week.  Took half a year to get through one fight).

2. Saiyuki, because I watch (listen) to the english dub.  And when the last two series of it changed voice actors, well, the damn thing just felt odd, leaving a bad taste in my mouth.  Speaking of, it's probably the 2nd longest series that I own.

3.  This one is the real kicker.  My all time favorite anime (best soundtrack too).  FLCL!!!  What can I say about this anime that is my favorite of ever?  Six episodes only!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  I wanted more and I still wish I could get what I want, but I will be forever stuck with 6 episodes of a legendary anime.  And I guess I'm ultimately fine with that.

On a side note, I rememeber being in a store for over an hour, asking myself if I wanted to buy the FLCL dvds.  It would cost me 60 bucks and tax for six episodes, and I did it, duh.  Now I have the BluRay copy.   =P

Anime with too many episodes i actually hate: Pinocchio

This is a very difficult one to answer.
Surely if it's your least favourite anime then you won't bother to watch it...
How about I specify genre: Reverse Harem and Magical Girl jump to mind.

Bartender is an essay in pretentiousness

I'm currently watching Durarara as it airs on Adult Swim, and it seems to be moving too slowly for my tastes, though i'll give it another month or so to see if it goes anywhere good...