Often, a manga and its respective anime adaptation can both be praised and enjoyed by fans. However, there are instances where this isn't the case -- and the manga is considered better than its animated counterpart. For some series, the manga doesn't need to add filler, where an anime needs to build a buffer between the source material.
Unfortunately, other series fail to adapt their source material correctly or even provide an enjoyable experience at all. From entirely unfaithful adaptations to manga stories that have been mangled by lousy CGI, these following anime -- in one way or another -- are the worst of the worst when it comes to adaptations.
One of the most infamous modern anime is Berserk (2016), the latest adaptation of Kentaro Miura's classic manga. While it adapts the Conviction story arc, even saying that paints an unrealistic expectation since it's such a disappointing series. The series is well known for its horrendous CGI, with the stilted anime's visuals resembling a Playstation 2 era game.
The subpar animation and camera work make the show borderline unwatchable. Likewise, none of the nuance or drama of the source material can be taken seriously. Simply sticking to the manga would be a much better option in this case.
Kare Kano is considered by many to be a classic in the slice-of-life and romance genres of manga, though its anime adaptation isn't nearly as well received. It started well enough, but production cuts led to a disastrous final set of episodes toward the last half of the series. The result was a somewhat childish-looking crayon art style for many scenes, making do with the available budget -- not going with how grounded the actual story was.
Likewise, the mangaka didn't like how the series became more focused on comedy instead of the serious topics of the source material. The manga would continue for several years after the anime ended, meaning half of the series wouldn't be adapted since the anime wouldn't continue.
The Promised Neverland
The Promised Neverland was an incredibly well-received manga, and the first season of the anime was no different. This made fan anticipation for the show's return through the roof, but unfortunately, the second season was a mere letdown at the absolute best of times.
It notoriously skipped huge chunks of the manga, and what it used was poorly paced and not nearly developed enough. Massive reveals and big character moments weren't given the aplomb and nuance required to make them stick like in the manga, and the whole affair just felt rushed. Most notably, the ending was an even worse version of what was already criticized about the manga's conclusion. Forcing everything into a second, conclusive season also means that another season can't be made to fix this one's mistakes.
Another offender of the crime of horrendous CGI is EX-ARM, based on the manga from HiRock and Shinya Komi. The cyberpunk crime series dealt with futuristic technology and the blurring lines between man and machine. Like the aforementioned Berserk, none of these themes can be taken seriously in the anime version due to how distractingly disappointing the visuals are.
Despite receiving financial funding from Crunchyroll, the show's use of CGI -- which was questionable anyway -- is atrocious. The character movements are unnatural, causing all of the show's "exciting" action scenes to be entirely cringeworthy. These visuals also ruined some pretty pivotal scenes, gaining the show even more notoriety.
Flowers of Evil
The Flowers of Evil was a powerful manga beyond its mere slice-of-life trappings, dealing with various issues of adolescence that are otherwise overlooked. This, unfortunately, didn't save its infamous anime adaption. For one thing, the anime tries to play up the tension of many of the story's events, making what should be seen as harmless pranks into almost life-or-death situations. This choice ultimately makes the main cast feel unlikable.
Perhaps the show's biggest sin, however, is the ever-present issue of its animation. The series is made via rotoscoping, giving the look of placing anime aesthetics onto realistic-looking people's faces. The effect is downright creepy, with the issue of the uncanny valley making the show difficult to sit through. Unfortunately, the rest of the show doesn't help its case, making those who want to enjoy the story better off reading the manga.