Many things that can kill an anime experience for its viewer. If there are too many unfunny running gags, insufferable characters or meandering plotlines, one may be inclined to drop the series altogether. This can happen all too often in the world of anime, even for successful series.
The sad thing is that these anime aren't necessarily otherwise bad. They do plenty of the right things and have good ideas that would work well in a better series. Some of them are that better series but fail to live up to their own name. The choices they make end up frustrating viewers because they know how good such a series can be and it's painful to see them fail. Here are some examples of anime that people want to like but can't always bring themselves to do.
1) Gundam SEED Destiny
Gundam SEED tells a familiar enough story for Gundam fans. The advanced humans who live in space colonies, the Coordinators, are at war with the ordinary humans of Earth, the Naturals. The show tackles themes of war and hatred, and of mankind's efforts to move past them both. As far as Gundam anime go, it tells a decent enough story with a concrete beginning, middle and end.
Gundam SEED works fine as a self-contained story, so adding to it would be gratuitous. Despite its functionality storywise, Sunrise saw fit to ride on SEED's success and give it a sequel series, Gundam SEED Destiny. Unfortunately, Destiny seems to take away more from SEED than it adds. So many choices for this series conflict with its predecessor; one couple loses their relationship for absurd reasons and doesn't exactly get back together; the new cast is unlikeable and constantly fights with the old cast; the main characters survive their mobile suits exploding, something hard to swallow in any incarnation of Gundam. If Destiny had somehow been its own story entirely and didn't stain the legacy of SEED, it might not be held in as much contempt for its shortcomings.
2) Black Clover
Black Clover's anime has gotten pretty good over time, but manga readers will tell a much different story. The series revolves around Asta, a peasant boy with no magic of his own who works hard to become a Magic Knight and, someday, the Wizard King. It relies heavily on tropes commonly found in shonen battle series, but it executes them well. What's more, it relies on the viewers' familiarity with its story elements to relay the plot at a breakneck pace.
The anime technically goes by fast. In fact, it nearly caught up to the manga before Studio Pierrot put it on hiatus. However, manga readers definitely notice the difference. The anime pads its 20 minutes-per-episode runtime by repeating mediocre running gags over and over and drawing out scenes excessively. Moreover, at the start of the series, Asta's voice is exceedingly grating. The anime's handling of the source material can easily kill the experience for some. Thankfully, it still does well in terms of animation, music and other elements that make it watchable for anime fans.
3) Attack on Titan: Junior High
Attack on Titan is one of the best anime out there, but that doesn't necessarily translate over to its spinoff material. Junior High takes characters from the main series and places them all in a slice-of-life comedy. The series takes its cast, key plot elements and even whole chunks of dialogue and applies them to lighthearted middle school antics.
Sadly, the series isn't nearly as good as it should be. Since Junior High aired between Seasons 1 and 2 of Attack on Titan, the spinoff draws material almost exclusively from the first season. As a result, many of the gags end up getting reused ad nauseam, like Ymir saying she and Krista should get married or Oluo biting his tongue. This material can turn stale fast. It's a shame because some of the references are used to great effect and can get a genuine laugh out of fans who understand them. It's (almost) enough to wonder how they would have handled material from later seasons.
4) Food Wars!: Shokugeki no Soma (The Final Arc)
Food Wars follows the story of Soma Yukihira as he undergoes cookoffs against the elite students of Totsuki Culinary Academy. This series should have ended shortly after the events of The Fourth Plate where Soma and his friends challenge the Totsuki Elite Ten Council. Unfortunately, the heads of Shonen Jump insisted that the manga go on a little longer because sales were so high, leading to the most ridiculous, annoying and disappointing arc in all of Food Wars.
Very little about Food Wars' final arc feels necessary. For one thing, many of the new cooks that Soma faces all have superhuman skills and abilities, which takes away the fun of replicating their dishes in real life. Several cookoffs among minor characters also happen offscreen (presumably because the chef who was supposed to advise the writer was on maternal leave). What's really annoying, however, is that everybody Soma faces in this arc is a meanspirited gatekeeper; these sorts of characters exist throughout Food Wars, but, given Soma's accomplishments, he shouldn't have to put up with it. This finale to an otherwise brilliant series is both inane and unpleasant.
5) Dragon Ball GT
Dragon Ball GT is a prime example of a series that's great in concept but poor in execution. The series has so many good ideas for its main storylines: a search for Dragon Balls across the universe; previous villains coming back from the dead to wreak havoc; the Dragon Balls themselves turning into the final antagonistic force of the series. All of these are good setups for great Dragon Ball stories, but they're bogged down by the gaping plotholes, uninteresting fights and bad character choices. Whatever nuggets of good that can be found in this series have now been written off as non-canon by many, along with all the nonsense surrounding them.
