I don't think there's any anime I won't enjoy while I'm watching it. It's kind of something I subconsciously do so that I can get through it because I refuse to drop a series before I finish it, unless I'm just starting it.
In the same way, I don't like to drop series once I've started, if only because I would always question whether it actually got good later on. I've even watched sequels when I hated the original. Hasn't paid off yet, but oh well.
I'm not really going to talk about genres that I hate. For instance, I could name a dozen harems that I don't like, but that's because I don't like harems. Instead, I'll focus on ones that I just genuinely didn't like.
Fair warning, I give reasons for why I don't like each anime. Reasons means
heavy spoilers. Obviously, I don't recommend watching any of these, but if you still plan to, be advised that the spoilers are there.
Amnesia:
Where do I even begin with this one. I get that it's supposed to be some kind of romance fantasy aimed at the female audience, but I honestly don't know why. Absolutely none of the characters, main or otherwise, is likable at all. Between the cold academic who is dating her as a social experiment, to the crazy that is trying to woo her one moment and strangle her the next, I honestly don't understand the supposed attraction. The best is the yellow guy (didn't bother learning their names when they are so helpfully color coded), who seems like an actually caring and loving guy. I was thinking, "well, she finally got a decent guy." That's when he started drugging her and locking her in a cage. I should also mention that they didn't even bother naming the main character. When referenced, she is simply called Heroine. Absolute rubbish of an anime. The
opening song was pretty good at least. Ironically, I actually found this anime through
osu.
Diabolik lovers:
The awkward level of this anime was beyond most that I've ever seen. I'll start off by saying that it's a vampire anime. That's fine, there have been some good vampire anime in the past. This one, however, is quite bad. There's little to no plot. Actually, there's quite a bit of it. There are a lot of flashbacks that introduce pointless characters that are never seen or mentioned again. There are a lot of mysteries that are introduced but never touched on or resolved. There are a lot of plot twists that are never explained at all, and really make no difference because nothing ends up happening anyways. The only thing that ever does happen in this anime is that the main character is held down and drained of blood every time one of the vampires ever sees her. The way it was portrayed was comparable to rape. Not only awkward, but the whole thing was despicable. Of all the hundred or so anime that I have watched, I can easily say that this was the most boring waste of my time out of all of them. At least the episodes were only 10 min long. Much more, and I would have gone insane with this one.
Ergo Proxy:
I don't like this one because there was so much potential that was just wasted. The first few episodes, there was this amazing, yet terrifying cyberpunk world, with mysteries and plot abound. After that, I'm not sure what happened. Most of the rest of the anime is of them sailing a boat through a desert. Yeah, it's atmospheric and portrays a dystopian world where all that is left outside is wasteland and devastation, but that doesn't make for an interesting story. Most of the anime felt like filler, and then there was filler for the filler. There was one episode where the characters found themselves in a game show with no explanation, and I swear, there was more plot in this filler episode than the two before and the two after combined. Just a waste of time.
.hack SIGN:
I had to force myself to sit through this one. Hell, I dropped it twice before finally finishing it a year after starting it, and it's only 26 episodes long. It's just boring. I really have nothing else to say about this one, because nothing really happened. Maybe the other series in the .hack franchise were better. I'll never know though, because SIGN was so bad.
E: I should mention that I didn't hate it because it was wordy. I've watched shows like Bakemonogatari, one of the most wordy anime of all time, and actually enjoyed them a lot. Honestly, the whole monogatari franchise, in general, has been one of my favorites of all time, with the exception of the most recent season, though I blame the fact that they tried to bring in harem elements, when that was never really an important part of the series. My point is, it's not that SIGN is wordy, it's that the plot quite literally goes nowhere, and all the wordiness is just talking for the sake of talking without accomplishing anything at all.
Shingeki no Kyojin:
I once heard this one described as having a death fetish. That's pretty accurate, and it't not a good thing. I'm fine with death in an anime. Death is a powerful plot device. It can make the difference between an anime with a powerful story that persists in memory and one that is simply good (Kyoukai no Kanata, I'm looking at you). On the other hand, a plot device as powerful as that should be used sparingly, as it can easily loose it's potency. It got to a point where I didn't even bother learning names because I knew, with certainty, that they would die in the next few episodes. I was never once proven wrong. The funny thing is, a lot of people say that this anime is really good because it has no plot armor. I would disagree. If by no plot armor, you mean Erin dying, and then coming back from the dead, or Mikasa being portrayed as some kind of invincible wonder being that fights titans for fun, or Armin, who has come so close to dying a dozen times and always manages to survive, then sure. There was a lot of hype for this one, but personally, I hated it. Agree or disagree, I would still recommend skipping this one.
Honestly, there are more that I didn't like, but these are the ones that I had to force myself to sit through, for whatever reason.