There are a host of reasons why some anime and manga endings are bad. Sometimes it's production issues. Other times, the mangaka suffers burnout; likewise, the anime might overrun the manga and have nothing to adapt.
There are plenty of examples from across the decades of fumbled endings, many of which are subjective to personal opinion. This list is no exception, as there are many reasons why these 10 endings made fans and non-fans alike abandon these series faster than Sonic the Hedgehog can run.
Disclaimer: This list is subject to the author's opinion. Likewise, beware of spoilers for all the endings of the anime discussed, including some recent anime.
Attack on Titan and 9 other anime and manga with badly executed endings
1) Akame Ga Kill!
Akame Ga Kill was a victim of overrunning the manga, as the anime was ongoing when the manga was still being released. Specifically, the anime was being produced roughly three years before the manga ended. This resulted in a somewhat botched ending that pleased no one.
The notable part about the anime's ending is the severe number of deaths starting in episode 20 and onward towards the end. This includes Tatsumi, one of the main characters dying trying to save civilians.
Likewise, the number of contradictions that are pulled (powers being able to do things they shouldn't, characters having knowledge they shouldn't, etc.) brings the ending of the anime down to one of the worst, according to reviewers.
2) Neon Genesis Evangelion
So, the original Neon Genesis Evangelion ended rather weirdly. As in the original TV series, the end came right out of nowhere. This has more to do with production issues than anything else, as Studio Gainax was infamous for having budget problems.
The final two episodes are best described as some weird high school alternate universe, with heavy amounts of stock footage and philosophical ruminations. The infamous "Congratulations!" scene is part of it too.
Though the End of Evangelion movie effectively supplanted this ending, it was no prize. At least Shinji wasn't alone in an empty void in the movie, though his first real action, attempting to choke out Asuka, didn't win any favors. Of course, the manga isn't any better on this front, seemingly erasing all the problems in favor of magical amnesia using a time skip.
3) Attack on Titan
This is an odd one to talk about, considering how many people were put off entirely by the end of the manga. To put it in the most basic way possible, Eren Yeager attempts to pull a Lelouch gambit from Code Geass, only for everything to be revealed in the last few chapters to be basically all for naught. The explanation also comes right out of nowhere.
Eren was essentially a prisoner of fate. He was bound to the idea that if his friends killed him, they'd be heroes to the rest of the world. While the ending and extra pages imply that's what happened, unfortunately, many fans didn't buy into it.
It's seen as forgiving mass genocide, racism, and all manner of terrible subjects, with Paradis still being reduced to rubble and the massive tree at the end implying the entire nightmare starts anew! At least the extra fake preview with modern-looking Armin, Mikasa, and Eren in chapter 139 extra pages was a heartwarming send-off.
4) Dragon Ball GT
This might be a controversial example, but Dragon Ball GT is considered the black sheep of the Dragon Ball franchise for a reason. Whether it's turning Goku into a kid, a few botched arcs, or just the ending, many people find a reason to ignore this chapter of Dragon Ball and jump right into Super. The ending itself doesn't help matters.
At the end of the Shadow Dragon Saga, Goku decides to leave along with Shenron. This might be a good idea in a "fix the planet yourselves" type of way, if not for the fact that it doesn't feel earned as much. GT's ultimate problems come down to execution, and its ending felt incredibly rushed.
5) The Promised Neverland
Speaking of rushed finales, The Promised Neverland's end and second season, in general, could fill a book as to how it tripped over itself. At the end of the first season, the orphans fled to freedom from the terrible, demon-sacrificing orphanage they were in. It felt like a victory that was earned, and many manga fans tuned in to see what would transpire.
Instead, the anime decided to commit several cardinal sins others on this list have committed: skipping entire story arcs, many characters left out, Isabella lives to redeem herself, the demonic nobles are never fought, etc. Basically, the ending left people wanting, as nothing major felt accomplished after the first season. It was a downward spiral.
6) Wonder Egg Priority
A more befitting descriptor of a downward spiral into oblivion, to the point where many fans don't consider the ending canon, is Wonder Egg Priority. The esoteric happy ending here is due to many reveals and key issues that never resolve themselves. To put a fine point on it, it was a cliffhanger ending that opted out of answering many questions it posed and ruined the friendships between the four main girls.
The show itself may deal with complex subjects but reduces it to an evil AI controlling everything and everyone instead of continuing to examine the societal reasons behind the problems of suicide. The last-minute twist of Koito being shown to have accidentally fallen to her death and not truly being a victim of a teacher's advances also left a bad taste in many mouths. Plus, the final OVA was mostly a recap.
7) Soul Eater
For as much as fans loved Soul Eater in anime and manga form, the anime's ending left plenty to be desired. To wit, Soul Eater has mostly emphasized teamwork and strategy over any other shonen cliche of being the strongest person alive, but the ending seems to contradict this in a huge way.
While the manga ended with the Kishin sealed into the moon with Crona after the heroes' best efforts, the anime decided to take a different tack. Instead, Maka ends up punching Asura in the face and defeating him with some previously unforeseen "bravery and hope" trait that was never shown. It contradicted what came before and felt like a Dues Ex Machina.
8)Tokyo Ghoul √A.
Cliffhanger finales are never fun, especially when there's no guarantee of a follow-up. Tokyo Ghoul √A. is rather infamous for this type of ending. This strays into an odd territory, given that the manga was recreated almost scene-for-scene for a few episodes, but then suddenly, it deviates hard.
The manga was still going, but the anime decided to not only kill Hide out of nowhere but also cut out a lot of epic fights like Kaneki vs. Arima, among others. It left off with Kaneki carrying Hide's body, and that was it. Needless to say, that form of wrap-up left much to be desired.
9) Darling in the Franxx
The word for Darling in the FRANXX's finale is divisive, to say the least. The last five episodes have been declared non-canon by fans of the series. The basic setup is there, with children using giant mecha to fight monsters, but the problem is the seemingly last-minute additions of certain aspects.
There was plenty to criticize, from Zero-Two going into a coma to random alien invasions to Zero-Two and Hiro being reincarnated centuries in the future. Even for a Cloverworks/Studio Trigger/A-1 Pictures collaboration, wherein Trigger is known for weird things, the fact that plenty of things came out of left field really hurt this anime. It was to the point where Trigger's next animation SSSS GRIDMAN was considered a return to form.
10) Fena Pirate Princess
A recently released anime with an ending that feels out of place isn't something new. The anime's premise, a swashbuckling adventure on the high seas starring a kidnapped princess, seemed promising. Then roughly halfway through the series, it switched genres into a more supernatural story about Fena herself being a witch and a lot of other concepts.
This wouldn't necessarily make the finale a bad one per se if certain things weren't done. For one, having Fena have agency in the plot and story would've been nice. Ultimately making everything in her life the decisions of outside forces was a misstep, as was her being forced to sacrifice her memories in the end. It felt like the story writers couldn't decide on things.