Note: This article lists examples which take place within fandoms; not the TV Trope's opinion as to whether a change is for the worse. TV Trope doesn't have opinions. The focus is on over-reaction about minor changes.
As a general rule, any time the translated version of an Anime or Manga makes any deviation from the original dialogue, it is likely to draw this reaction from some portion of the fandom. While there are often very legitimate reasons for fans to be less than pleased with a translation, many within the fandom will still be upset even when the changes are relatively minor or more effective than a literal translation.
The DiC dub of Sailor Moon has a multitude of hatesites dedicated to it, by people who claimed to get up early to watch it when they were little, for any change made by the dubbers. After the license switched from DiC to Cloverway (though with the same studio, Optimum, still handling production), there are fans that still cry foul over the new translation team opting to keep the Japanese BGM in episodes, as they had been used to the DiC music and felt it was more appropriate. The inconsistent translations and dub terminology also didn't help matters, nor did the recasting of a few characters (Sailor Moon, Sailor Mercury, and Sailor Venus in particular).
There's also a vocal subset of fans who hate the anime for changing stuff from the original manga. Common criticisms tend to be the amount of Filler episodes and Padding added to keep the show from Overtaking The Manga.
Many Detective Conan fans were outraged about the name changes and the title change to Case Closed in the English release.
Digimon gets this almost every season. A new cast? No partner digimon? No digivolving?note This is even worse considering that evolution actually was introduced into the series later on.NOGOGGLES?! Judging by how many times it's been ruined, you would think the series had died years ago.
Fans often complain due to slight changes in manga and anime version of Brotherhood, especially in pacing (early episodes tended to be cut down significantly so the show could get to the stuff that wasn't a retread faster). Also fans of both the manga and original anime often have this about the art style of the newer series.
The English dub of Code Geass has fallen into receiving complaining. Lelouch/Zero's voice, in particular, is a point of contention, due in large part to his English VA not sounding enough like his Japanese one. However, there are at least some Japanese fans who seem to prefer Johnny Yong Bosch's over the top and hammy performance over Jun Fukuyama's performance, which they consider to be monotone.
There are many Tengen Toppa Gurren Lagann fans that had this reaction towards translations of show terminology that didn't match up with what was currently in use among the already-existing fandom at the time. There was also some discontent about the switch from Brett Weaver to Kyle Hebert as the voice actor for Kamina when the license for the show changed hands from ADV to Bandai.
∀ Gundam received a poor reception among the Gundam fandom, due to having little in common with the "classic" gundam style used by the rest of the franchise.
Nearly every important SEED character had at least 3 (Athrun and Lacus had at least 4-6 apiece) different romanizations of their names, some of these are still in use over the official English transliterations.
When Gundam 00 came around, the fans were against the idea that the new instalment would include aliens (which, up to that point, had been a non-entity in the Gundam franchise), and that the Gundams lacked "signature features" of Gundam designs, like mouth vents.
Mobile Suit Gundam AGE, in addition to the complaint about the inclusion of aliensthat aren't actually aliens but regular Humans colonisers abandoned by Earth on Mars that happen to have weird Mobile Suits, generated discontent for being more child-oriented than other Gundam series.
The anime adaptation of the gameValkyria Chronicles has received a lot of flak from fans of the game for some admittedly fair reasons: character exaggeration, key characters (Leon and Kreis) being omitted, mood whiplash, changes to key events (Lupus and Batomys), changes to some characters, an unwanted love triangle shoe-horned in. And for some not so fair reasons: having the squads at 10 men each rather than 20, getting the armour wrong, not including certain recruitables in squad 7, putting some characters in the wrong 'classes' they were listed as in the game.
3.0. received an even stronger case of this from fans, due to taking the Lighter and Softer feel from the last two movies and throwing it straight into Darker and Edgier territory, taking the plot in a way virtually no one anticipated... Long story short, it drastically turned everything into a direction that Evangelion has never experienced before.
One Piece received complaints regarding the English voices from 4Kids' dub of the series not fitting with the Japanese voices (the alterations to dialogue would be a different trope entirely). Later, when the license changed hands from 4Kids to Funimation, a different section of the fanbase criticized the Funimation voices for not matching the ones 4Kids used.
Admittedly, some of the fanbase's grievances with Studio DEEN's adaptation of Umineko no Naku Koro ni are legitimate. But when you have people complaining that they used the wrong music in a scene, you know this trope has struck with a vengeance. On the other hand, the Umineko soundtrack is one of the most amazing things ever written. Umineko's original visual novel received a PS3 port, fans of the original novel are upset to see the original artwork being replaced by more professional and detailed images. Fans of both series dislike the slight change in art style from Higurashi to Umineko, saying it looks even worse than the Narm Charm ridden Higurashi. Higurashi no Naku Koro ni fans dislike the changes DEEN did to the anime a lot, since it changes the way you see the story and the way the story is played out. The manga is far better received.
Death Note fandom splits less than equally into fans who think the scene on the roof is the best thing ever, and those who don't know what the anime producers were thinking. The anime ending has also been the subject of some debate, with some fans finding it ridiculous and others beautiful.
The first two seasons of Dragon Ball Z were dubbed into English by The Ocean Group while being licensed by FUNimation, and the English dub handled and controlled by Saban Entertainment; however, the show suffered from poor time slot placement and didn't get a lot of mainstream exposure until it began airing on the Cartoon Network, and then its popularity exploded. To meet the high demand for more episodes, FUNi made plans to dub the rest of the series, but broke off their connection with Saban, and realized realized it would be more economical to produce an in-house dub at their own facilities in Texas rather than outsource the work to Ocean in Canada, which they could no longer afford without Saban's funding. As a result, all the character voices in the third season sounded radically different from those in the previous two (before they were redubbed that is), creating a fiery backlash among viewers who had been fans of Ocean's work. To be fair, Funi's voice work at this time was admittedly pretty lousy, although they have since gotten better (see: Fullmetal Alchemist); rumour has it that they were recruiting people off the street with no prior VA experience during auditions, Frieza was voiced by a woman, and Puar and Chiaotzu were voiced by a librarian. However, while many of the voice actors had no prior experience in voice acting, most were to some extent. Sonny Strait (Krillin) had even voiced the original TOM on Toonami before his stint in DBZ.
The English dub of Monster by Viz has taken some heat for changing the music (regardless of how it's still all the original show's music, just that some of it has been moved), and translating a name as Lunge, when it's generally agreed that Runge is the accurate version due to being a real German name. The major argument against this is that we're lucky the series even got a dub with its huge number of characters and episodes. Later when it was pointed out that all foreign adaptations feature these music changes, fans still blamed Viz for not trying hard enough to get the original track.
Pokémon has one of the worst fanbases out there. It is a common belief that absolutely everything about the new episodes sucks, and that the tiniest changes will ruin the show. New Pokémon? Ruined. New voice actors? Ruined forever. A new female companion? You better believe it's ruined. Team Rocket changed their motto? Ruined. Now and forever. Team Rocket are badass now? You guessed it!note There is a small but vocal group that is up in arms about how Team Rocket got boring because their personalities are changed to very serious and driven, rather than bumbling and humorous, and that they have stopped showing up in every episode and many times when they do, they don't actually play a part in Ash's current story. Both Pokémon Special and Pokémon get this reaction in multiple ways when compared to the games. Be it the plot, the moves, the characterization... The eye retcons in Pokémon Best Wishes. Oddly no one minded the change in Pokémon Special, and the change was actually praised in the games (albeit occasionally you'll find fans who prefer the older 90s style). In the case of Pokémon Special, it helps that it's a black and white manga and that no one really paid much attention when only a very few got their eye color changed.
Saint Seiya Omega. The style changes in the characters design, the "future" storyline, the stepdown in the mythos concepts, the cloths changed from physical existence to gems projections...in fact, this whole leaded to a still on-going Broken Base war between "classic version" followers and the supporters of the Omega version
Surprisingly, not many complaints have been made about Nanoha's barrier jacket having its red ribbon replaced with some brooch for The Movie adaptation of the 1st season.
You'll get a lot more complaints from fans about who got wrote out of the movie, however.
The Wandering Son anime gets a lot of this from fans of the manga. At first it just came from the art style. Compared to other adaptations, especially Aoi Hana which is by the same author, the anime simplifies the style for ease of animation, with some fans disliking the changes. Character designs were also changed, many characters received Adaptation Dye Jobs and different eye colors in the anime, going from realistic colors to a wide range of fantastic ones. As a story, the series suffers from being very different from the manga. Chronological order is changed, the series begins In Medias Res which doesn't work for a manga driven by continuity and Kudzu Plot, Out-of-Character Moment scenes are added, scenes are changed, and the ending of the anime is dramatically different from its equivalent of the manga. It drives more of a "can't change your sex, and you'll just grow out of this" moral, which is in stark contrast to the manga, and to how many transsexuals feel in real life. Nitori's reaction at the end of the manga is vastly different in the anime. In the anime he takes a girl's comment about his voice changing with a stride and a true smile, while in the manga his reaction is dull and in shock; no smile either.
The anime adaptation of Aoi Hana is not off the hook either, though. Where killing most of the sub-plots does help to streamline the narrative, it also demolishes a lot of background about the relationship between Akira and Fumi, both in the present time as in their past. This leaves quite a few viewers not acquainted with the manga wondering just what the hell cheery Akira sees in Fumi, who gets across as a whiny, spineless brat without much characterization.
This is why the OVA to Escaflowne was very badly-received by fans. The movie is a Re Tool of the series. For example, Hitomi was originally an ordinary, rather jovial high school girl, but became an Emo Teen in the movie, and that upset a lot of people. If you find yourself in the company of Escaflowne fans, it's best not to discuss the movie.
It's not uncommon to see Pretty Cure fans tear apart the upcoming season due to character designs, plot, and even how the logo looks, all before the season has even aired, with one subset of fans constantly insisting that the series needs to go back to how it was in 2004 before the changes in newer seasons "ruined" everything. This also extends to the Pretty Cure All Stars movie series - people were not happy when they learned that New Stage was reducing 11 of the 28 featured Cures to The Voiceless and The Cameo, when they had speaking parts of the original. This is also compounded with how DX3 was pretty much so action packed and rather fair in speaking roles despite the tons of Cures featured it becomes such a Tough Act to Follow.
The English dub for Bleach gets this a lot. From "shinigami" to "soul reaper", Ulquiorra's softer, more deadpan voice or how some of the English voice actors sound a little different from their Japanese counterparts. It might just be a tie between which gets more fan backlash: the difference in Hollow-Ichigo's roar or any changes in voice actors that occur over the course of the show.
Studio DEEN's adaptation of "Buon San Valentino" of Axis Powers Hetalia, while providing enjoyment for some fans, was controversial in cutting out Prussia's part (explaining why Germany received a dating guide that only served to embarrass him), as well as any screentime for England and America. It also removed the final strip, in which a flashback draws a connection between Germany and Holy Roman Empire both giving Italy flowers.
Aku no Hana: Very much the most vocal complaint of the anime. Some fans claimed the use of rotoscoping was ugly and ruined their enjoyment. In addition, claims of changing the mood of the show to a quieter tone and redesigning the characters were also detrimental. The manga's creator has since vocally supported the changes and states he oversaw many of them.
Due to its age and multiple adaptations, Science Ninja Team Gatchaman has had cases of its own vocal fan complaints and criticism over time:
The animation style and music in Gatchaman II and Fighter are considered inferior to the original series, as the sequels used a brighter color palette that fans felt looked too gaudy and the background music was felt to be too overpowering. The design of the New God Phoenix also received criticism, due to it looking more overdone and childish.
The 3-episode OVA remake in 1994 isn't looked upon too highly due to it utterly redesigning all the characters, including giving Dr. Nambu a ridiculous pompadour and pink suit.
Gatchaman Crowds looks to be the ultimate example, as though it is considered part of the franchise, the complete re-imagining of the concept and lack of any of the recognizable cast (save for a redesigned Berg Katze, and a heroic version of Leader X who is an AI) left fans feeling it was an In Name Only off-shoot made as a cheap cash-in. The changes most controversial include the complete elimination of the bird motif from the team's uniforms, the warriors gaining their powers from spiritual beings instead of being well-trained and having some vague futuristic technology, the true leader of the team being an alien panda mascot, and the terminology changes ("Science Ninja Team" to "G-Crew"). And then there's the complete overhaul of Katze's origin, in which he's an alien and a former Gatchaman who went rogue, which some fans decried as ruining the show.
UQ Holder is basically a sequel series to Mahou Sensei Negima!, with a supporting character, Evangeline, from Negima becoming a secondary protagonist in UQ Holder. All well and good. Popular, even. Then there's the fact that Evangeline's adult form underwent a minor redesign (she has a different hairstyle and slightly different facial structure), and her personality is notably more mellowed out, and she goes by the alias "Yukihime". This kicked off a bit of a Broken Base between fans of Negima who think this trope is in play and that "Yukihime" is so differentiated from Evangeline that she might as well be a different character, and fans of Negima who attribute the changes to Art Evolution and the fact that UQ Holder takes place 80 years after Negima ended.
Attack on Titan suffers from this in the anime adaptation, especially in the second half. While some changes were welcomed because they provided more screentime or characterization without changing the overall story, the changes to the Female Titan arc have caused considerable debate among manga fans. This especially concerns the omitting of a key scene between Eren and Annie, as well as major changes to the last three episodes.
Tenchi Muyo! has problems due to multiple alternate universes, revivals, and retconning. Major flak comes for the Ryo-Ohki 3 OVA which was made 8 years after Ryo-Ohki 1 and 2 ended. It has so many retcons to characters' fates that it can be summed with the song "Everything You Know is Wrong". Tenchi Muyo GXP and War on Geminar also are belong to the Ryo-Ohki universe, despite not having the series' title character Tenchi or any other main characters actually in them more than cameos.