The Ice King receives no end of sympathy from most fans, continually painting him as harmless and misunderstood. While he is a Jerkass Woobie with a Freudian Excuse, he still harasses, stalks, kidnaps, imprisons, mind-controls, and at one point mutilates around a dozen different women, all for the purpose of forcing them to "marry" him.
Ash, Marceline's Jerkass ex-boyfriend, who unlike this previous two is a completely straight example - he's good-looking, and that's his one positive attribute.
While Lemongrab 1 was intended to be a Hate Sink, he still has fans. Yup, he has a loud fanbase that often forgot just why everyone hates him so much. Even after being revealed he uses his mental illness as an excuse to be a jerkass to everyone (when Lemonjon got Empathy), eating and mutilating his own brother, and finally becoming a corpulentdictator, his fanbase still tries to get everyone to sympathize with him despite revelations showing he doesn't deserve it - that sympathy is better spent on his brother Lemongrab 2, or their joint reincarnation Lemongrab 3.
Mozenrath from Aladdin: The Series. For many fans, his hotness and him being one of the better written and more threatening villains in the show outweigh the fact that he's sadistic, turned his father-figure into a zombie, devoted his life to ruining Aladdin's, and wants to take over Agrabah just "because it's there". The belief that Mozenrath was intended to be Aladdin's brother seems to be an unfortunate (and persistent) side-effect of this trope.
Azula is a callous cruel manipulator who kills without hesitation and gleefully advances the aims of the genocidal Fire Nation, but thanks to being the best example of Evil Is Sexy and Magnificent Bastardry in the show she has a large chunk of fans who insist she's a tragic woobie or just misunderstood. The Grand Finale gives her one hell of a Freudian Excuse and the following canonical comics hint that she might be redeemable after all, but the bulk of the DILP treatment started long before this, and it doesn't excuse her actions.
Zhao and Ozai get this treatment by Fire Nation fans for Evil Is Cool reasons, but unlike Azula they have no redeeming qualities whatsoever.
Sozin gets this treatment quite a bit, another case of his fans focusing on the "well-intentioned" and ignoring the "extremist" aspects of Well-Intentioned Extremist. They see nothing wrong with him wanting to spread the fire nation's glory, power, and advanced civilization with the rest of the world, which apparently justifies 100 years of war, the first act of which after disposing of the only man who could stop him was a complete genocide, and many other genocidal actions to follow. It's worth noting that Sozin himself comes to regret these actions even before he dies, and Iroh specifically states that Zuko, more on him below, has the opportunity to not only change his own path, but to cleanse the royal family's sins going back to Sozin.
Zuko got this treatment back when he was an Anti-Villain, with many fans saying all his wrong actions can be excused because of his angsty backstory and conflicted nature. Mike and Bryan themselves have brought this up in commentary for episodes such as "The Warriors of Kyoshi" and "The Beach" that, as sympathetic as Zuko is, he's not supposed to be justified in his bad actions, and in fact a big part of his Character Development is learning that he needs to take responsibility for his bad actions. This internal struggle of good and evil, which has still crept up even after his HeelFace Turn, is kind of the entire point of his character.
Long Feng and his Dai Li are sometimes given this treatment, with their Orwellian methods and repression of Ba Sing Se painted as the act of true patriots who were compelled to do whatever it took to keep their city safe. Case in point.
Happens In-Universe in the episode The Ember Island Players. The Gaang watch The Boy in the Iceberg, a play about their adventures performed by the titular Ember Island Players. The play is Fire Nation propaganda, and so it puts the Fire Nation in a much better light than the series does.
Play!Azula lacks most of the real Azula's psychopathy and mental instability. She doesn't shoot Iroh in the play's version of The Chase (she instead tells the others to Go Look at the Distraction and escapes through a hidden door), and she keeps her sanity throughout the finale, unlike the real Azula, who had a spectacular breakdown.
Play!Ozai still wants to conquer the world and kills Aang in the finale, but he has no plans of genocide and merely uses the comet for a power boost in his fight against Play!Aang.
Back at the Barnyard: Dag could be justified by the fact that coyotes have to eat, but did he really have to antagonize that one farm in particular, kill Ben, make Otis feel small, and attack during the day when no one was expecting them?
Fanfics about Batman: The Animated Series often depict the Rogues Gallery as a fun-loving bunch of lovable misfits who are unfairly and brutally harassed by the humorless Caped Crusader. Never mind that even in the kids' show's context, most of the Rogues were originally apprehended for attempting ruthless murders on hapless civilians for imagined or exaggerated slights, and that when Batman was put on trial for supposedly creating his foes, the jury of villains found him not guilty in the end and decided that they were responsible for their own messed-up behavior. Then they tried to kill Batman anyway.
The Penguin also gets the Jerkass Woobie treatment: it's easy to feel sorry for a short, funny-looking man who gets looked down on by many people. This is particularly the case in the early episode "Birds of a Feather", where it's shown that he commits crimes (all of them as nonviolent as he can possibly make them, unless he gets really angry) either simply for fun or to win some respect for himself. That episode even opens with him speaking politely and amicably to a man he's just tied up and is robbing. It's clear, at least in these early appearances, that the Penguin doesn't want to hurt anyone; it's just that he feels being a crook is what he was meant to do in life.
Mister Freeze is another villain who gets this a lot, due to being a Tragic Villain. And while he does have redeeming features, he also happens to be The Unfettered, obsessed with revenge, and in some appearances a Straw Nihilist who targets innocents just to spread his own misery.
Harley Quinn also for being an abuse victim at the Joker's hands, and actually having her origin shown in which he manipulates her into becoming his accomplice by taking advantage of her obvious crushon him by feeding her sob stories. While this is genuinely tragic, it does not excuse her numerous homicidal acts as a part of the Joker's entourage. Her first appearance has her gleefully try to bomb the policeman ball while all officers present are paralyzed by a toxic gas, and she becomes willingly complicit in several more severe crimes form then on.
After Alien Force made Kevin a good guy, this trope went to his new Evil Counterpart Darkstar instead. Darkstar is a pure creepy Jerkass stalker who had no problem with manipulating innocent schoolgirls and turning them into zombies to increase his powers and is never portrayed as sympathetic in any way, even during his Enemy Mine with the heroes. Other villains like Vilgax, Charmcaster, Albedo, and the Forever Knights at least have varying shades of nobility and moral ambiguity to them. Darkstar has none.
Lahwhinie from the Chip 'n Dale: Rescue Rangers episode "Gadget Goes Hawaiian" is Gadget's Evil Twin. Period. At least in canon. But for some fans, she is Gadget minus her quirks and geek attitude and lack of social skills, but plus a dress and make-up and actual passion, and sometimes have her do a more or less spectacular HeelFace Turn.
Code Lyoko: William's long-term possession by XANA has definitely increased his fanbase, although the emphasis is more on curing him than on loving him for/despite being evil.
Vlad Masters/Plasmius based his life around revenge for an accident and the title character's father "stealing" his one true love Maddie. He uses deception and mind control to amass his fortune and uses it and his ghost powers to attempt murder and cause mayhem, which he somehow thinks is a good way to get Maddie to fall in love with him and Danny to consider him as a better father than Jack. Yet because all he wants, essentially, is to be loved, numerous fans ignore that he's a selfish, maniacal narcissist.
In fact, in a reality where he did get what he wanted, marrying Maddie, he still became a bitter, controlling man, to the point where Maddie threw him into the ghost zone.
Ember McLain gets this treatment, mostly for her loss, but some fans think that her song was about her suicide after being cheated on by her Bastard Boyfriend. It helps that she (and several other members of Dannys Rogues Gallery, for that matter) is increasingly portrayed as fighting Danny for fun more than out of malice.
Mandark from Dexter's Laboratory In the show he's an Evil Genius and the closest this series has to a Big Bad. Try explaining that to fangirls who portray him as a sweet nerdy boy who just wants Dee Dee to love him.
Duck Dodgers: Deconstructed in one episode. There's a villain called the Magnificent Rogue who basically terrorizes people, yet is worshipped because he's so attractive. Even when he flat out admits that he is indeed insane. Porky snaps out of it and ultimately thwarts his plot. IQ also states that being beautiful doesn't give you the right to terrorize people. It could easily be trying to mock this trope.
Eddy gets a lot of this. Fans use his Freudian Excuse involving his brother as a legitimate excuse for how badly he treats his friends and the other kids in the series. This is ignoring the fact that most of Eddy's jerkass behavior is done out of free will, as Eddy sometimes starts unprovoked drama with the the other Cul-De-Sac kids. Fans would even go as far as to attempt to push the blame off of Eddy by putting all the blame solely on the other characters for their roles they played against Eddy and his actions (just go to the videos (especially the Youtube comments on said videos) and the comments of the episode pages of "A Case of Ed" and "Brother, Can You Spare an Ed" and you'll see a lot of whitewashing/ignoring of Eddy's behavior).
May Kanker is often seen as a sympathetic Woobie and the Token Good Teammate of the Kanker sisters (a trio of bullies/molesters and the main villains of the show). True, the way her sisters treat her sometimes puts her on The Woobie territory, but when it comes to other people, she's just as cruel as them. Yet, some people would rather believe she wouldn't hurt a fly and she's just oppressed by Marie and Lee.
Her sister Marie, being the prettiest Kanker, usually gets the free pass from fandom, alternatively given a Freudian Excuse, similar to May's example above. It's also easy to find comments (especially youtube comments) about Edd being an idiot for rejecting a "hot" girl like Marie.
Even Lee occasionally gets this treatment in fanart along with her sisters, but less often than May and Marie.
Norm from The Fairly Oddparents gets this bad. He's often portrayed as The Woobie, locked up in his lamp and was forced to serve several masters like Timmy. This is ignoring the fact that he is a Card CarryingJerkass and such a Jackass Genie that he was that page's picture. Also, he had tried to sell Timmy (who was originally apathetic toward Norm) on the prospect of having a genie, and the fact that he plans to destroy Canada once he's free should erode his sympathy.
Vicky is a destructive, abusive sociopath, but so many of her fans go to incredible lengths to justify or outright ignore these traits. Others simply fabricate a Freudian Excuse for her out of thin air, despite being repeatedly established that she has no such excuse, and indeed is the Freudian Excuse for several other characters, Timmy included. Disturbingly, there are even people who ship her with Timmy.
Anti-Cosmo who's Cosmo's evil counter part, has been seen as a fairy who simply wants his own godchild, baring the fact he has made several attempts on conquering or destroying Fairy World and Earth.
Family Guy: Stewie tends to get sympathetic treatment in later episodes, largely due to putting up with Brian's selfish egotism and his Comedic Sociopath parents, disregarding the fact that even following his Flanderization, Stewie is often portrayed as a sadist who tries to kill his mother and puts Brian through all sorts of painful stunts for petty slights or even just to see if he can. (eg, giving him two gangster style beatings for overdue gambling fees or travelling in time to sabotage every meaningful point in his life over a gay joke).
And to mentioned even now and then, he's still shown to commit manslaughter or even outright/attempt murder on occasions.
Hexxus, the Spirit of Destruction and pollution embodied in FernGully: The Last Rainforest gets this even though he's trying to level a rainforest full of plant and animal life as well as sentient fairies that depend on its existence to survive. It doesn't help that the movie is Anvilicious, the protagonists (save maybe for BattyKoda) are bland and rather uninteresting, and Hexxus himself is voiced by Tim Curry, with all the implications this entails. And he gets one of the best Villain Songs of all times.
Demona. While the character is definitely a three-dimensional villain, and you understand where she is coming from, a lot of fanfic authors spin this off into either being an apologist or completely re-writing the character to the point where she is Demona in name only. Add in the fact that she's already somewhat sympathetic by design and there you go. Usually, her daughter Angela will either wave a finger in Demona's face, and Demona magically gives up her hatred to have a relationship with her, or Demona magically falls in love with a human and sees that humans are not all bad. A lot of the time, Goliath is portrayed as an evilmisogynist. Generally, most of these fanfics are just an excuse to get Demona naked, and some authors have admitted that canon Demona is too difficult to write. Word of God states that Demona will still be plotting against humanity long after Angela and most of the cast are dead.
While Xanatos does get a whole slew of Pet the Dog moments and arguably evolves into an Anti-Villain by the end, he still commits a lot of ruthless or downright evil acts (especially early on) and never seriously regrets any of them (except maybe creating Thailog). There are nonetheless a disturbing amount of fans who portray Xanatos as little worse than a brilliant trickster, with more than one declaration that he isn't really evil or villainous. This probably wouldn't happen half as often if he didn't look like a physically-idealized Jonathan Frakes.
Rounding out the trifetica of the show's major villains is Macbeth. He's easily the most sympathetic even in canon- he's as tragic as Demona but not a tenth as vicious, and as affable as Xanatos without being nearly as manipulative- and he has an old-school warrior's sense of honor, but his fans have a definite tendency to treat him as a Hero Antagonist, which several of his actions (notably deciding to use Broadway- with whom he had no personal quarrel- as target practice for newly-acquired spells) show he's not. Per Word of God, he's an ends-justify-the-means kind of guy, and his ends are pretty questionable on their own. Character Development, however, does end up moving him into Hero Antagonist territory by the end of the series.
The only recurring villains who aren't in some way sympathetic are Tony Dracon and Sevarius, and they sometimes get the DILP treatment.
Breach. She isn't without sympathetic qualities, but sometimes people forget that she's completely insane and has happily kidnapped people to use them as toys in her "playhouse," throwing them away when she gets bored of them.
Murdoc of the Gorillaz is often seen this way, despite being a canonically alcoholic, exhibitionist, verbally and physically abusive megalomaniac. The trope is even employed in-universe, since despite many of these traits being publicly known, Murdoc does not lack for bedmates.
Bill Cipher, the Big Bad of the entire series. He is a living embodiment of the Illuminati symbol and he has psychotic behavior but fans love him. He is often drawn as a sexy man with one eye covered and dapper clothes who is sometimes shipped with Dipper or Mabel. Back in "Dreamscaperers," most of his villainous acts technically took place inside dreams, yet he still showed signs of his chaos-loving like when he telekinetically removed a deer's teeth to creep out Gideon. Fans ignored the warning signs and thought his mysteriousness at the time was hinting at some kind of morally-gray character, beginning to make all kinds of romantic interpretations of him. When the episode "Sock Opera" where he possesses Dipper's body debuted, fans started fawning over "Bipper" and outright calling him sexy even though he tried to kill Mabel. Even when the last quarter of the series makes it blatantly clear that his "strange plan" is to destroy the world for fun, which he partially succeeds at doing (he manages to cause an apocalypse in the town of Gravity Falls, but he's stopped from going further by a barrier), the habit of painting him as some sort of misunderstood good guy persisted to the end of the series and pairing him with the Pines remained some of the most popular ships in the entire fandom.
The episode "Soos and the Real Girl" had .GIFfany for its Monster of the Week, who is a sentient Dating Sim character. She is a Yandere who is implied to have killed her developers and tried to kill the people who played her, she also tries to force Soos to upload his brain to her system so they can be together forever. When he refuses to let her upload him, she outright threatens to kill him too. Many people found her cute and sexy and were even attracted to her yandere tendencies since she "proved" she was willing to go a long way for love, even if it meant coercing and abusing the person she "loved." She even gets some of this in-universe: the entry Soos wrote about her in Gravity Falls: Journal 3 has him praising parts of her game after she tried to kill him and saying that she's sweet when she's not trying to kill people, hoping that she wasn't killed in their battle. She wasn't, as being made of energy meant she couldn't be destroyed and is just safely stuck inside the arcade now.
Happy Tree Friends fandom does this with Evil Flippy, insisting that he's really just misunderstood and needs "twu wuv", or his good side in order to become an upstanding member of society. Never mind that they've already got Good Flippy to toy with.
Helga Pataki. In the series she's a Jerkass Woobie with a Hidden Heart of Gold who is horribly neglected by her parents, but who also can be mean, selfish, rude (and even cruel in some instances) does many things moved by jealousy and constantly bullies other kids (not only Arnold). However, despite that, many fanfics (especially romantic fanfics) portray her almost as a saint. This happens mostly because a lot of viewers see themselves in her, a sentiment amplified by her main character status.
Curly is pretty much criminally insane, but many fanfics downplay it for various reasons.
According to some of his fans Zim is really a totally badass mastermind. But don't worry, he's not really evil; he would seriously regret destroying humanity, and would probably give it up if a kind-hearted human or Irken girl would just show him some love. Oh, and also, isn't Dib just such a bastard for trying to stop him so much? There's a bit of this for other Irkens too, particularly the Tallests. Apparently galactic conquest and repeated genocide and enslavement of the survivors is a-okay.
Gaz. Simply put, she's a selfish, abusive, and greedy brat with absolutely no redeeming qualities, yet many fans praise her as "the smartest character on the show" and call her a no-nonsense badass. This is especially baffling when you consider that not only does she refuse to risk her life for anyone but herself, but that she only goes after people who are much weaker and for petty reasons. Notably, the creator himself ended up regretting how horrible he had made Gaz, and in both the comic series and Enter the Florpus movie she is rewritten to be an actual badass who actually does have redeeming traits such as care for her brother.
Kaeloo: Mr. Cat is portrayed on the show as a psychopath who wouldn't hesitate to kill or maim people for petty reasons, and also is a selfish, greedy, rude, egomaniacal, sarcastic jerkass. In fanon, he is portrayed as much nicer, and some fanworks even portray him as a sweet person who just wants Kaeloo to love him.
Amon is the charismatic leader of the Equalists, who just want to bring about equality between benders and non-benders by ending all bending, but have absolutely no problem harming the very people they claim to be helping. Amon's so charismatic that he's managed to convince some of the fans, who rightly point out existing inequalities in Republic City, but tend to gloss over that forcibly stripping people of something the setting treats as intrinsic to one's soul is not a nice thing to do.
Tahno, while eventually becoming somewhat sympathetic after Amon takes his bending and leaves him a broken man, had fans wishing he could give them "private lessons" even when he was a total Jerkass.
Season 4 gives us Kuvira. She desperately wanted to save the Earth Kingdom from falling into anarchy after The Earth Queen's assassination. To that end, she usurped power from the reigning Prince Wu and reformed the kingdom into the Earth Empire. Like Amon, she is extremely charismatic and can justify her actions with arguments so reasonable that even the heroes begrudgingly agree she has a point. So charismatic is she that even some of the fandom will defend her by saying that she's just doing what she thinks is right, even when it's revealed she is throwing those not of Earth Kingdom decent into labor camps. The fact that the series finale portrays her as a Woobie, Destroyer of Worlds and gives her a Freudian Excuse to further humanize her only reinforced this sentiment.
The Loud House: An unusual case where this is applied to the main character of the show itself, Lincoln Loud. Fan-rewrites or Fix Fics of unpopular episodes where Lincoln gets the short end of the stick often portray Lincoln as an innocent victim of the torment of his sisters (who are often given the Ron the Death Eater treatment) who calls them out for their mistreatment of him when in the canon episode(s) Lincoln wasn't entirely blameless or even brought on the torment upon himself. It's especially noticeable in certain re-writes of the widely-disliked episode "No Such Luck", where Lincoln calls out his entire family for treating him like dirt because they thought he was a jinx (sometimes to the point of getting them arrested or otherwise punishing them), even though in the actual episode, Lincoln, like it or not, brought everything bad that happened to him upon himself by making his family believe that he was a jinx solely for his own gain.
Even though the sisters are given Ron the Death Eater treatment, there are also a good number of fans who give them Draco In Leather Pants treatment as well. Many go too far in defending them, even when they DO act horribly.
In Mega Man, RS-Protoman is arguably not as bad as most of the examples on this page, but some fans seem to think that his switching alliances would instantly rid him of his less pleasant traits. (Possibly so they can offload them to their idealized version of RS-Bass).
The more sympathetic akumas tend to get this treatment, despite the fact that, no matter their reasons for getting akumatized, they're still villains who work for the Big Bad and are completely willing to harm innocents.
Hawk Mothhimself started getting this treatment once it was revealed that he's Gabriel Agreste. Fans latched on to his concern for Adrien's safety and motives (bringing his beloved wife back), while ignoring the fact that he often puts Adrien in danger to begin with.
Both of the show's alpha bitches, Chloe and Lila, have been getting this from fans:
For Chloe, it started becoming more justified when the writers tried to give her Character Development and turn her into a superhero; however, she constantly displayed Aesop Amnesia in regards to this, and if anything only got worse in season 3, where she willingly worked with Hawk Moth because Ladybug didn't give in to her demands. Despite this (or perhaps because of it), the fans love having her see the error of her ways and become a good person for real. Usually, fans actually at least address her flaws and have her work to overcome them (though they sometimes make it too easy for her), but there are writers who just brush them aside.
For Lila, while it was more understandable when we only had "Volpina" to go by in terms of her personality (with there being enough wiggle room to give her constant lying a Freudian Excuse), there are still fans willing to do this after she's proven herself to be a sociopath who is perfectly willing to work with a supervillain to get what she wants. They usually excuse her behavior by claiming that Ladybug was partly responsible for her downfall as she humiliated her in front of Adrien, that she was manipulated and encouraged by Hawk Moth, that she clearly suffers from her parents' constant absence, and that she actually has feelings for Adrien, meaning she can't be a heartless person.
Scarab from Mummies Alive!. Never mind that he was something like a cross between Mr. Burns and Mumm-Ra; Fan Fic still has him suavely hooking up with heroes of the show alike. Considering that relatively few people even remember the show, the sheer amount of Slash Fic it generates around an aging Corrupt Corporate Executive who powers up into an insectoid monstrosity is rather disturbing.
The Sirens/The Dazzlings are this for My Little Pony: Equestria Girls as a whole. They're the most popular villains from the franchise by a country mile, and they often get portrayed in fan works much more sympathetically than their canon counterparts. Since very little is revealed about their backstories, fans have taken semi-canon sources (like the Fiendship is Magic comic book on them) or just made up their own backstories for them. The Sirens are often made out to be lost souls, sisters who have no one but each other, ageless beings who are now forced to Walk the Earth with nothing, Tragic Monsters who don't want to feed on hate but have no choice, or showing remorse for the things they've done. In canon, the Sirens are a Terrible Trio who want to spread a Hate Plague, caused people to be brainwashed against their friends, and show absolutely no remorse for any of it. Even in their appearance in Sunset's Backstage Pass, the Sirens don't have a Heel Realization; the closest they get is admitting their plans failed, and they're just as nasty as they ever were. It's rare to find a fan work that tries to stay in line with the canon portrayal of the Sirens as villains, and even rarer to find someone who actively dislikes them.
Rico. Okay, so he's not evil, but he is a loose cannon who needs to be kept under tight control. All that craziness is very often tossed aside in the interests of pairing him up with whichever penguin the author chooses.
King Julien. He's not evil, but he is a jerk. Again, it's abandoned for the purposes of bedding him down with Skipper or Marlene. The weird thing is, the movie, while he's not all that nice, he at least is concerned for his subjects, and demonstrates sincere gratitude toward Alex and the others, but is listed under Jerkass. While in the series he's abusive to Mort and Maurice, malicious toward the Penguins for the sake of it, rude in general and self-serving, with his few decent moments usually having at least partially selfish motivation, yet is listed under Jerk with a Heart of Gold, despite his negative qualities far outweighing his arguable positive ones.
The Rowdyruff Boys tend to be toned down and glamorized into being misunderstood little boys who secretly long to be loved and in relationships with the Powerpuff Girls, the only ones who can tame them. Series creator Craig McCracken grew so frustrated with this phenomenon that he came to regret bringing the Rowdyruff Boys Back from the Dead and left them out of the series' Ten-Year Anniversary episode out of spite, despite every other major member of the girls' Rogues Gallery appearing.
Out of all the boys, Boomer seems to be getting this due to the constant bullying that his brothers put him through. They claim that he has empathy for others, forgetting the fact that when it comes to other people, Boomer is just as bad as his brothers.
Fans sympathize with Princess wanting to be a Powerpuff Girl and always getting rejected, ignoring how she doesn't have superpowers or crime fighting experience, and only cares about being a Powerpuff Girl for the cosmetic reasons (being popular, powerful, and loved) and the fact that even if the Powerpuff Girls DID consider adding extra members to the team, Princess certainly wouldn't make the cut due to her spoiled rotten behavior.
The Gangreen Gang get this to an extent. Some people in the fandom portray them as these innocent boys whom the world and their families have outcasted for no good reason; and while the show has suggested here and there that the team might have some good in them (like when they helped the girls take down Sedusa, or how they changed sides in the FusionFall game), they're still delinquent, disrespectful teens who vandalize the city and prey on children and the elderly just for kicks.
Rick and Morty: Rick Sanchez, one of the title characters of the show, is typically an asshole of many calibers. He's a drunk, selfish and reckless, even if he can get him and his grandson Morty out of sticky situations (though he's the one that normally put them in said situations). Every once in a while though, Rick seems to have a moment of character development, and fans forget that he's an asshole. Even if immediately after the moment of character development, he reverts back to his normal asshole-ish self.
Besides, he has a loud fanbase that sympathize with him for being Made of Evil. He simply CAN'T stop being evil because it's in his very nature to be evil. The fact that some fans saw his death as a Tear Jerker moment of the series only cemented this status, since his death marks the end to an iconic Cartoon Network villain many grew up with. Of course, this is ignoring that Aku is a Chaotic Evilsadist whose list of crimes can fill a book; and his sense of humor aside, he has no redeemable traits. Some fans even consider him as Ugly Cute or Creepy Cute, largely due to his somewhat simplistic design.
The Simpsons has Sideshow Bob. While his intelligence, menacing aura, and highbrow/Deadpan Snarker attitude combined with the perpetual clown-like mishaps to which he's subjected make him a cool and funny villain, there is a considerable fanbase determined to overlook that his life revolves around murdering Bart and those who stand in the way of his murdering Bart, instead making him into an angster hiding his suffering under an antisocial exterior. Extra annoying in that they overlook the canonical explanation for any angst (his being Krusty the Klown's Butt-Monkey for years), instead giving him a depressingly cliched tragic backstory.
The South Park fandom does this a lot, especially with characters like Cartman, who once tricked a kid into eating his parents, and Damien, who set Pip on fire and turned Kenny into a duck-billed platypus.
Plankton in Spongebob Squarepants. It has been established that he's evil as he continued to try to take Krabs' secret formula in myriad ways. One episode even had him as a Jerk with a Heart of Jerk with him saying "Being evil is just too much fun!" His actions include enslaving Spongebob, taking out his brain, and gleefully attempting to murder people several times. He's definitely crossed the Moral Event Horizon. But because Mr. Krabs Took a Level in Jerkass in later seasons, a lot of folks act as though Plankton is some innocent victim who never does anything wrong, when even in those seasons he's still a Jerkass who has done just as many nasty things as Krabs has. Obviously that doesn't excuse what Krabs did in "One Coarse Meal", but still...
Squidward could also fall as an example. Sure he suffers a lot, but there are fans who ignore all the bad stuff he has done and treat him like an innocent victim, even when some of his misfortunes are brought upon himself.
Star Wars: The Clone Wars has some. Since Darth Maul was brought back in the fourth season, he has fans (as seen with the films). General Grievous, although he's a cold-blooded cyborg who killed hundreds of people receives this in spades. Young!Boba Fett also gets this, though in fairness, he's portrayed during his appearances as a sympathetic character.
While Superjail! has a cast filled with characters that are corrupt or despicable to some degree, there are a few examples that tend to stand out when it comes to this:
Some tend to ignore the fact that while Alice has a bit of an unfortunate backstory, she's also described by the creators as a sadistic bully who intentionally abuses her power to get herself pleasure from the inmates. Any of her flaws can get easily glossed over for her to be simplified and painted as a saintly Woobie who just needs one good man (when fans aren't going in the other direction to demonize her for not returning Warden's feelings).
Lord Stingray gets a bunch of this treatment from certain fans, who feel as if he's been unfairly wronged and misunderstood for being imprisoned in Superjail. Some decide to depict him as physically attractive in order to play up suaveness to make him a viable partner for the Warden, if they don't go with outright Foe Yay.
The Twins are sometimes simplified into harmless innocent young men who just want to have fun in the jail, even though they're shown to take visible amusement in causing death and destruction. Sure, they start trouble to relieve boredom, but they aren't any less questionable in their morality than the rest of the cast.
Dr. Viper in SWAT Kats has a few fans despite being arguably the series' most sick, twisted and sadistic villain in his very first episode alone, and not being what would generally be considered attractive (even before he got mutated). Many early fanfics by one "Kikki Viper" revolved around the evil biochemist converting to Christianity, gaining a magical sword and saving the day. The fanfics have been given the MST treatment by many a SWAT Kats fan. Artist Ignigeno sexifies Viper while at least retaining his evil, sadistic personality.
Varian from Tangled: The Series was an Ensemble Dark Horse when he made his debut as an Adorkable, sympathetic alchemist and ally to Rapunzel. Then he went offthe deepend, and fangirls started making excuses for his behavior ("He's trying to save his father! He can't be that bad!"), ignoring the fact that a) most of what happened was his own fault, and b) his end goal didn't excuse a number of the atrocities he'd committed, up to and including attempted murder. As if to reinforce that this was missing the point, following his HeelFace Turn in Season 3 Varian himself constantly emphasizes that he was the only one to blame for his wrongdoings, even having a whole song about it as he's trying to talk a Face Heel Turned Cassandra down from her path.
Shredder from Teenage Mutant Ninja Turtles (1987) has a lot of fangirls. In fact, of every single incarnation of Ninja Turtles, his version is considered the most popular/sexiest of them all in spite of the fact that he's a misanthrope who wants to take over the world and regularly threatens to consume four teenage sentient lifebeings simply for trying to deter his plans. Many are drawn to his voice, his body, his outfit and, depending on the animation, the fact that he's rather handsome without his mask on (something that is played up a lot in canary and fanfics).
Agent Bishop from Teenage Mutant Ninja Turtles (2003). Compared to the Shredder, he's a much more sympathetic and well intentioned villain, however while an undeniably a complex villain a lot of fans definitely romanticise him a little too much, especially considering the countless acts of murder, espionage, torture, and other dirty dealings that come close to, if not outright rival, the Shredder's. By the sixth season, set decades into the future, Bishop does renounce his evil ways to become one of the good guys, so he's not an entirely unsympathetic or irredeemable character. However, he achieved DILP status far before "Fast Forward" and there are still a disturbingly large amount of fans who prefer to sweep all his evil deeds under the rug and act as if he's nothing more than a heroic savior of the world with no flaws.
Slade, whose intelligence, competency and "cool" factor results in many fans ignoring the fact that he's a mind-raping adult who takes pride in stalking and fighting teenagers. Some fans even go as far as to find him blameless for Terra betraying the Titans. While yes, it was partially Terra's fault, Slade still played a role in it. Fans even go as far as to make him innocent compared to Terra.
There's a subset of fans who think Terra should have been welcomed back with open arms and accepted as a permanent member of the team even after her stint as The Mole and The Dragon to Slade. They argue that none of it was her fault since Slade manipulated her (Terra herself makes this argument, but Beast Boy points out that she could have gotten out at any time but chose not to, and Terra ends up redeeming herself by acceptingthis and taking responsibility). She's a sympathetic Woobie, Destroyer of Worlds to be sure, but to paint her as a blameless martyr is missing the point of her character (of course, but so is painting her as an irredeemable fiend like other fans like to do, which is just as bad, and if not worse).
Smudger from the Thomas the Tank Engine episode, "Granpuff" has a lot of fans who want to see him return to the series. This is despite the fact that he was a naughty, arrogant engine who often rode too roughly and never learnt from his mistakes, as well as the fact that he's been turned into a generator for life, and the Mid Sodor Railway is closed by now.
Tygra from ThunderCats (2011), the reboot of the 1985 series. While he does have his share of redeeming qualities, is one of the good guys, and is confirmed by the creators to be a Jerkass Woobie instead of a tamed version of Big Brother Bully, a lot of his fan are a bit too willing to forgive him for and justify him leaving his adopted brother, Lion-O, to die twice, being somewhat of an unapologetic bigot, undermining Lion-O's authority and not supporting him on occasions.
Duncan. It's invariably difficult to keep him in character seeing as his softer side overrules his bad-boy charm in the eyes of most fans. If you find a fanfic involving Duncan/Courtney, Duncan/Gwen, Duncan/anybody expect Draco in Leather Pants to come into play. (Although, those that ship him with Gwen do have some justified argument, she is the only one he is rather nice to.)
Gwen and Courtney also have this problem. Some fans on different sides of the CxDxG conflict believe the girl they support is blameless while demonizing the opposing character.
Most of the villains get this treatment. There are some fans who will portray Scott as kinder for the sake of someone (to be fair, this canonically happened in Season 5), and even Mal (a.k.a. THE MALEVOLENT ONE!!!) is portrayed as having a shred of goodness in him in some fanon, despite being essentially MPD Mike's inner embodiment of chaotic evil.
Ezekiel is occasionally written as a sad, down-on-his-luck, poor woobie who doesn't actually want to be in the game, and gets a lot of flack from other characters who never forgive him for his sexist comments back in the first season saying that guys are better than girls. By season three, and hinted at since the post-elimination special of the first season, it's clear that he's actually incredibly arrogant and there are more reasons for people to not like him besides his comments (which nobody really brings up to him). Seeing as he clings on to the jumbo jet after being thrown off and willingly stays there until becoming feral, it's also obvious that wanting to leave the game is something he would never do. And yet the innocent, pull-toque-over-his-eyes Ezekiel is still present after all of this, probably because the creator's attempts to make Ezekiel come off as a Jerkass with a huge ego backfired in his fan's eyes due to how little screentime he got... And how divided fans are over how he eventually became an expy of Gollum by the end of World Tour and the fact that two seasons later, he still hasn't fully recovered. It also helps that a lot of his more arrogant actions can easily be seen as a desperate attempt to get people to like him.
Decepticons as a whole can be called Robots in Leather Pants. It's about a 50/50 split and Deceptifans tend to downplay their villainy a lot. Notable examples include Starscream, Ravage (especially after his upgrade in Beast Wars), BW Rampage, Animated, Starscream, Lockdown, Megatron, and more of Starscream. Megs tends to be viewed as a misunderstood anarchist, a la Axel Rose, and even inversions where Optimus Prime is depicted as a self-righteous fascist are not entirely unheard of.
It started with Beast Wars; technically, the Predacons are an oppressed minority on a "peaceful" Cybertron kept in the paranoid grip of the just-as-atrocious Maximal Elders, but their role is more akin to between-World Wars Germany, with Megatron and his troupe attempting to get them to put on the Reich. Like the Animated Decepticons, this goes unnoticed by fans, blinded by Beast!Megatron's Magnificent Bastardry, Tarantulas' delightful craziness, Waspinator's Butt-Monkey-ness...
The Transformers Armada incarnation of Starscream is pretty much entirely remembered for the period he defected to the Autobots. Based on how people talk about it, you'd think it happened in the first episode and he served the good guys with honorable conviction, as opposed to lasting a total of three episodes where his entire motivation was that he wanted to kill his boss and he thought it'd be more convenient to do so with allies. He does make a somewhat more genuine HeelFace Turn towards the end of the series, and even a Heroic Sacrifice, but even then, he was hardly the "hero on the wrong side" many refer to him as. Fans of the character also tend to toss his later Energon and Cybertron appearances, where he was completely evil, into Fanon Discontinuity.
Transformers Animated deepened this. The Decepticons in this series are in some ways oppressed resistance fighters trying to overthrow a regime that is outdated at best and downright corrupt at worst, but they're less "Rebel Alliance" and more "Al Qaeda". Fans tend to miss this part because Megatron is awesome, Blitzwing is funny, and Starscream is, well, Starscream.
Starscream's usual Draco in Leather Pants treatment is taken Up to Eleven in Prime. Because of his skinny physique and how badly he tends to get punished, fans are quick to paint him as a Jerkass Woobie and some even write Hurt Comfort Fics that ship him with his Arch-EnemyArcee, glossing over the many dogs he's kicked; said dog-kicking includes killing Cliffjumper and throwing his death in the other Autobots' faces whenever he can, threatening Miko in front of an immobile Bulkhead, and taunting a T-cog-less Bumblebee about his inability to transform while holding said T-cog at gunpoint right in front of him.
One-shot villain Madame Catastrophe from Tuff Puppy is often hit with this trope, usually being brainwashed instead of evil.
In the old Voltron cartoon, many girls adored the self-proclaimed evil Prince Lotor, despite his attempts not only to kidnap Princess Allura, kill the Voltron Force and raze her planet to a pile of ash, but also (and repeatedly) to force her into marriage, brainwash her, or commit various other despicable acts; he has never shown an ounce of remorse for any of this. Many fans will attempt to argue that he was forced to do this by his father, even though he hatched and enjoyed half these plans, and though he continued making them after he usurped his father. Others will say it's all out of love for Allura, even though he was willing to throw her away for another princess that looked just like her.
Things haven't changed much in Voltron: Legendary Defender, as Lotor's Adaptational Heroism and Woobie, Destroyer of Worlds backstory has allowed many a fangirl to excuse or overlook his systemic killing of Alteans in experiments over the years, Alteans who thoroughly trusted him and worshiped him as a savior which allowed them to happily walk to their deaths at his command. A common reaction for fangirls is anger that the Voltron Paladins turned on Lotor after learning this fact, to accuse Allura of just being racist against Lotor despite having genuinely been willing to enter a romantic relationship with Lotor despite his Galran heritage beforehand, or to accuse Romelle of somehow lying and making the whole story about experimental death camps up just to soil Lotor's good name even though Lotor himself admitted that it was all true and that he did it for what he believed to be the greater good.