Agent Grant Ward, who in the episode "Turn Turn Turn" is revealed to be a double agent working for Hydra. The character has drawn sympathy from abuse survivors under the Stand With Ward hashtag whom want him to be redeemed due to a perception that the media has often neglected or vilified abuse survivors. This is due to his sympathetic backstory. In the aforementioned episode, he outright murders Agent Hand and spends the next five episodes storming S.H.I.E.L.D. compounds and killing his former allies willy-nilly. It gets even worse late in season 2 where he has gone on to kill more people, brutally torture a member of Coulsen's team, laid a trap to kill even more SHIELD agents. He has even taken over HYDRA to avenge the murder of his girlfriend.
In fairness to Ward fans, Ward's characterization was all over the place. At least one behind the scenes interview post Season 1 confirmed Ward had genuinely come to care for his SHIELD teammates. Furthermore, early Season 2 clearly portrays him as The Atoner. In the second half of Season 2, he displays traits of both an Anti-Hero and an Anti-Villain. And throughout the season he makes frequent apologies and takes responsibility for his past actions. Ward being full-on evil in the Season 2 finale came out of nowhere in the eyes of his fans and his portrayal in Season 3 reduced him from being easily one of the most complex characters on the show to a Card-Carrying Villain. Of course, YMMV.
Though Dandy Mott is a Psychopathic Manchild whose also a serial killer that murdered his own mother and bathed in blood, that is not to say that there are some fans that sympathize with him. After all, there are rich people who have gotten bored in the past. He also claims that he identifies with the freaks, though in the final episode he decides that he's going to kill everyone (other than Bette and Dott), in the freak show. He also claims that he loves Bette and Dott, though it's doubtful that if he truly loved the Tattler twins he wouldn't have gone after their friends and family in the first place.
Lost: Ben Linus. While he is certainly intelligent, driven, and has his genuinely sympathetic moments here and there, he's also an unapologetic sociopath, manipulative, self-centered, and homicidal.
Adelei Niska from Firefly. This elderly sadistic crime boss is known for torturing his wife's nephew to death in one episode, and Mal and Wash nearly to death in another episode. But his wince-inducing torture techniques are contrasted by a unique personality and accent.
Daniel Grayson from Revenge. Many fans encourage a serious pairing between between Daniel and Emily, despite the fact that Emily only initially dates him to destroy his family and vindicate her father. Admittedly this desire was justifiable during the beginning of the series when Daniel was portrayed as a misguided but ultimately good guy who wanted to distance himself from the Grayson name. However, after Daniel finds out the truth about David Clark's framing and continues to cover it up, usurps his father as CEO from his own company via nepotism, steals majority share of Nolcorp for the fun of it, blackmails a man to get his vote and participates in framing Amanda for Helen Crowley's murder, considering his character someone Emily would ever genuinely date seems ludicrous.
Spike. Inadvertently lampshaded in the episode "Crush" when Dawn lists "he wears cool leather coats and stuff" as a reason she likes him.
The vampire fan club in "Lie To Me" is a good in-universe example.
There's another small example in "Crush", in the form of a female Watcher who has a crush on Spike.
After two seasons the main cast had become Shell Shocked Veterans, and that's when Faith is introduced, which turned out to be a much needed breath of fresh air after the Angelus plot. She was sassy like Buffy, not afraid to have fun, looked like a million bucks, even when she was with the good guys had a dark streak that she wasn't afraid to show, and her fight scenes were among the best in the series. Even when she turns into a killer she still had a large fan base, to the point where some fans blame Buffy for Faith turning the way she did.
Billy Mitchell was introduced to EastEnders as an abusive bastard who beat the living hell out of his nephew Jamie. For some unfathomable reason, fans liked him. He was slowly turned into a gentle, nice, and weak man who was given all the "touching" plot-lines about a nice man with a hard life, reducing the earlier child-abuse plotlines to being occasionally mentioned by his family and himself as a warning not to let his temper get the better of him, especially after he winds up with custody of a child, again. Still, that last bit means that he gets a little of this In-Universe, even if he's mostly reformed out of it in ours.
Sheriff Donald Lamb, whom some fans loved even though he was a petty, self-absorbed himbo slacker who ignored heroine Veronica Mars when she attempted to file a report on being drugged and raped. Series creator Rob Thomas and actor Michael Muhney acknowledged that they went overboard in the pilot in order to make Lamb an unlikeable jerk, and they even gave the character a sliver of sympathy by revealing that Lamb was abused as a child by his father; but Thomas refused to humanize Lamb or negate the events of the pilot (as many fans of the character had done via fanfictions). He had Lamb tell Veronica that he still didn't believe her claim of being raped and taunt her over the issue during season three. Thomas then had Lamb largely absent from season three's rape storyline and had his head bashed in during season three's second arc at the hands of a crystal meth addict (that last possibly because Lamb's fans wouldn't leave him alone).
Dick Casablancas encouraged his brother to rape Veronica, and yet the fanbase seems to adore him. The cast and crew have outright admitted to only keeping his character around for love of the actor that plays him, Ryan Hansen.
The Master, particularly in his Anthony Ainley and John Simm incarnations. In fan fiction, he's usually not portrayed as the murderous psychopath he is, but as just a mischievous, quirky, sexy guy who just wants to have some Foe Yay with the Doctor. "The End Of Time" which revealed that the drums which apparently drove the Master insane were planted as part of The Plan by the Time Lords has only made it easier for those inclined to ignore or handwave his lengthy list of evil deeds with the "it wasn't his fault, they made him do it, he's really a sweetie!" card. The Ainley version is also walking around in the body of Nyssa's father. Thus, every time the Doctor battles him, he's facing the man who murdered the father of a close friend (along with her entire race) who is also in that same man's body, which gets creepier the more you think about it.
In a case of a hero's shortcomings being overlooked, the Tenth Doctor was prone to inexcusable choices from the beginning of his tenure: deposing Harriet Jones for showing him up, "burning up a sun just to say goodbye" to Rose, then invalidating her later for not wanting to be lumbered with a clone, ignoring Donna's pleas to keep her memories, and treating Mickey and Martha awfully among other things. The worst part of all this is that he never seems to notice the error of his ways and always has to be portrayed as being in the right, even though some of his mistakes caused untold hardships for billions down the line (deposing Jones allowed both Harold Saxon and the almost as bad government of Torchwood: Children of Earth to come to power, spoiling what the Doctor knew to be a golden age for Britain). The fact he looks like David Tennant certainly seems to help his fangirls see him as more of a tortured, romantic hero rather than one whose Character Development was by and large negative. By comparison the Twelfth Doctor, who started as a Grumpy Old Man but became Lighter and Softer with time, was almost never let off the hook for less-than-ideal decisions no matter how well-meant, was punished for his selfish choices in the Series 9 endgame, and "died" as one of the most empathetic, loving, and self-sacrificing Doctors of all, is less popular and romanticized because he looks like Peter Capaldi.
A non-heroic example is Jack's murderous, psychopathic ex John Hart who, despite manipulating everyone for his own gain, bringing Jack's brother Gray to have his revenge, and setting off a chain of events that kills Owen and Tosh. Yet the fandom adores him and often claims his arguable love for Jack as a redeeming quality. Possibly a case of Evil Is Sexy as well.
As Gaius Baltar has his cult of rabid, beyond-reason believers in Battlestar Galactica, so does he have his cult of rabid, beyond-reason believers in the real world. It helps that no one on that show is cut-and-dry good or evil, but as far as selfish acts go, Gaius has performed many of the most shameless ones.
Weyoun. More subtly evil than the overshadowing Dukat, but to squealing fangirls (and boys), Weyoun is absolutely adorable. After all, he's not necessarily evil: he was programmed that way, and is capable of overcoming his programming. (We even see one such "defective" Weyoun in one of the episodes). Also, he's played by Jeffrey Combs.
Section 31, which, granted, gets the Ron the Death Eater treatment as well. It's a shadowy black ops organization intended to show that even the Federation has to get its hands dirty with black ops, introducing a deliberately complex moral question for the characters and fans. However, there are some who berate anyone who doesn't approve of every single thing Section 31 does, including their attempted genocide against the Changelings, ignoring the inherent He Who Fights Monsters question in favor of lauding all their actions as right and necessary and decrying anyone who disagrees as naive fools.
Alex Krycek from The X-Files. Krycek has betrayed (and tried to kill) Mulder and Scully on numerous occasions, but some fans think he and Mulder make a cute couple. Non-slash fans of the "Rat-boy" desperately tried to find excuses and claimed that it's all just a part of his elaborate plan of outsmarting the conspirators.
The character of Detective Ronnie Gardocki, on The Shield, developed a major cult following amongst fans of the show in spite of not receiving much screen time or character development during the first couple of seasons of the show outside the occasional nerd moment and Butt-Monkey-style physical abuse moment. As such, many fans of the character began promoting the notion/belief that Ronnie was a nerdy and all all-around good guy who simply fell in with the wrong crowd at work and not a rotten to the core corrupt cop whose soul was as black as the rest of the team. Needless to say, even when Ronnie is hauled off kicking and screaming for his crimes committed as part of the Strike Team (which has to be spelled out to him by Dutch, when he reacts in a confused fashion when he's arrested) at the end of the series, fans of the character argue that Ronnie was the victim, having been screwed over by Vic Mackey, who ratted out Ronnie for immunity for all of his crimes (including murdering a fellow cop) and a cushy new job with the Feds. Ironically, even David Rees Snell is aware of the trope that his character suffers from, as seen in the following interview.
Julian Sark from Alias is amoral, killing people left and right to further his own goals, and yet he still has a horde of infatuated fangirls ready to throw themselves at his feet without a second thought. They tend to swoon over his Pretty Boy looks, fashion sense, posh English accent, dry wit and keen intelligence.
Noah Bennet - legitimately loved as a Badass Normal and Magnificent Bastard - is nevertheless often happily excused of abducting and experimenting on people (including children) for about 17 years. And what convinced him to stop was essentially an extreme case of Protagonist-Centered Morality focused on his daughter Claire. Bennet's moral ambiguity is an unquestionable part of the character's appeal; the Draco in Leather Pants-ing comes in when fans use "but he's morally gray!" to handwave away any suggestion that Bennet might have crossed any ethical lines, or suggest that Bennet "didn't know any better" (this is especially odd coming from fans who love Bennet because he's one of the smartest and most competent characters on the show).
Cole Turner/Belthazar. Let's see. He's a demon, but "Cole" is his human half so, hey, he's not all that bad, right? He repeatedly plots against, deceives, considers killing, and attempts to kill the Charmed Ones, but he's really just misunderstood, see. Even when he was possessed by The Source, essentially Charmed's version of Satan, he's still just a big ol' softy to some viewers (and Phoebe, whose intelligence could be questioned to be perfectly fair she was being manipulated by the Seer who used her love against her then went through some fairly well scripted angst). Part of the dangers of casting Julian McMahon for your villain.
Cole's girlfriend Phoebe is a bit of a Draco herself as the above text demonstrates. The relationship with Cole going wrong is almost equally her fault as well yet her faults are easily ignored by fans. Cole tried to give up the Source's powers only for Phoebe to step in and kill the wizard who was willing to take them. When Cole returned, some fans treat her as perfectly justified in her treatment of him, ignoring that the reason he came back with new demonic powers was because she refused to bring him back to life when the alternative was him going to demonic hell. Add that to how she spends a lot more of the series abusing her powers, stringing guys along and fawning over her own beauty and you have yourself a DILP.
Appears in-universe in Lie to Me, where a serial rapist locked up in jail has a bunch of fans who attend his trials and parole hearings and act like they're witnessing the second coming of Jesus.
Scorpius from Farscape, despite his numerous Kick the Dog moments. It doesn't help that wears a bloody full body leather suit and is the embodiment of Affably Evil (until you really annoy him). In fact, he became so popular, that by the end of the third season he'd gotten his own sympathetic background and eventually joined the main cast as a pseudo-protagonist.
Todd Manning from One Life to Live. Gang-rape, terrorizing a blind woman and beating his teenage daughter's friends without any provocation aven't stopped him from becoming favorite among some aggressively protective "He's so hot!" fans. It's very much a case of Perverse Sexual Lust and the show doesn't help as Todd is almost inarguably this show's main character and they tend to load him up with humor and charm.
Stringer Bell from the The Wire. Despite being Avon Barksdale's right-hand man in crime, he was portrayed as intelligent, insightful, clever, and determined to learn how the legal business world worked, so that he could expand into honest projects. He's even shown taken community college courses. Because of this, fans saw him as a sympathetic character. They conveniently forget how he was the one who setup and got D'Angelo Barksdale killed off in prison, while at the same time, having an affair with his woman. They forget how he did this behind, Avon's back. They forget all the other backstabbing and under handed things he did. Which is why in the end, it caught up with him.
In Stargate SG-1, Ba'al is perhaps the best example of this. He kidnaps and tortures Colonel O'Neill, kills thousands of people, enslaves the human race (or tries to, anyway) and is generally a Manipulative Bastard, yet he's still so loved by even the most loyal fans. Why? To put it quite simply, he's hot. He also has a huge amount of charm and is quite funny, so despite being evil at heart, is still able to woo the audience into loving him.
It doesn't hurt that Ba'al is, while ruthless, nowhere near as despicable as most of the other Goa'uld in the show such as Apophis or Anubis. He has aided the good guys in the past against Anubis and the Replicators and has generally acted in an Affably Evil manner. Also, his stance on the Ori conflict, that the Ancients should be destroyed along with the Ori actually has a lot of merit given their aloofness and refusal to help even when problems they create (e.g. Anubis) threaten to destroy all life in the galaxy. Finally, even though he manipulates the timeline to become ruler of the galaxy in the Continuum movie, his intentions to form an alliance with Earth instead of enslaving it and grant freedom to the Jaffa before his being backstabbed by Qetesh seemed genuine. All in all Ba'al is a villain, but a nuanced one with many reasons to like him beyond his attractiveness and charm.
Anyone who attempts to turn you from a person who eats sentient beings into a person who does not is interfering with your civil rights, right? Michael Kenmore thinks so, and it appears much of the fanbase agrees. Obviously, anti-Wraith genocide, Wraith worshiping, or living like a cow herd is the better way to go. Keep in mind that at this point, the replacement food research was going absolutely nowhere. Being brainwashed and lied to is reasonably enough to make a person cranky and get some sympathy, but a lot of fans act like the Atlanteans did this to prevent Michael from performing his favorite folk dance out of spite. Why, yes, Michael, we DO think being a Wraith is a disease-how many people have died from you being a Wraith so far? Could we get some sympathy and righteous indignation for them?
Sympathy for Michael comes not from him being turned into a human, but from the criminally insane manner in which the Atlanteans treated him after his Heel–Face Turn against his own Hive to help *them*. Admittedly this was after the hive betrayed and ostracized him, however he genuinely believed the hive Queen wanted an alliance with the Atlanteans. His repayment for his aid? He was forcibly turned into a human and memory wiped AGAIN. This being after he technically forgave the Atlanteans for doing it to him the first time. It was only after this that he became a megalomaniacal sociopath hellbent on revenge.
Also, Todd the wraith. Yes, we know he fed on Colonel Sheppard. Yes, he's a wraith and eats people. He's also funny, gave John back the life he took from him and does in fact help them out several times, even if he's generally a jerk about it and winds up only doing it to further his own goals.
Star Trek: The Next Generation Lore, Data's Evil Twin, has received this treatment in fanfics. Apparently, people think that the love of a good woman is all it takes to redeem Lore, when he wouldn't even be redeemed for his own brother. One fanfic out there was, in its entirety, a "Lore For President" flier.
Eric Northman. He kills people left and right,runs a Torture Cellar holds humans in contempt, magically forces a woman to be sexually attracted to him and outright states he's fed on children and was a Viking, and not the kind that trades or explores. But somehow he's just misunderstood. You should see the contortions fangirls go through to excuse the fact that he idly stood by and watched while someone tried to murder the woman they chiefly pair him with. It's a bit worse than one might think: His fans try to brush that off with how different the times were back then. Yeah, try telling that one to all his victims. Then after getting literal Laser-Guided Amnesia and then regaining his memory, he becomes genuinely heroic when the Authority turns into a Cult for the Evil God Lillith. Bill, who up until this season was a 'hero' fully went villain due to seeing Lillith, while Eric experienced a My God, What Have I Done? after Godric breaks through the blood haze.
Franklin. On one hand he's a psychopath, but on the other he's handsome and has some funny one-liners. Compared to most of the other characters, he's surprisingly intelligent and capable of well thought out schemes, and was the only one of Tara's partners who called her out.
Darken Rahl from Legend of the Seeker. He commits mass infanticide, horribly tortures people to death in order to gain magical power, tortures them after death for information and for the heck of it and even beside that is an oppressive tyrant in slightly less Kick the Dog methods. But fangirls insist he had the good of the land at heart because of his self-aggrandizing speeches to the woman he was torturing.
The villains of Smallville. Lex Luthor, when he finally became evil around season 5/6, Davis in season 8 and Zod in season 9. Tess Mercer is a definite example in Season 8.
Lionel Luthor. Affable, witty, cultured and theMagnificent Bastard he may have been, but he was still emotionally abusive, self-centered and sociopathic for at least four seasons. Must have something to do with being played by John Glover.
Zero from Tin Man is a coward that gets his kicks torturing — well, lots of people, but notably children. And yet fangirls swoon over.
Furio in The Sopranos kind of falls into this, even canonically, as many fans (and Carmella Soprano) saw him as a cultured and sensitive Nice Guy. The issue is that while he kind of is in private life, on the job, he's a totally vicious and brutal thug.
Alec in Dark Angel somewhat. While he's a good guy by the end, the fangirls are far too forgiving of/willing to overlook his beginning on the side of evil or his time as an egocentric lawbreaker in the middle of the season. Likewise, Jensen Ackles' other character Ben (Alec's twin brother, the Serial Killer) is a lost and vulnerable puppy.
Craig gets excused for cheating on Ashley and stringing Manny along due to his Dark and Troubled Past. Not to mention, both of the girls get hated on more in the fandom than Craig is - either Ashley's too stuck up or Manny is a slut.
Jay pretty much ruins every life he touches by introducing drugs and alcohol into their lives, but he is still well liked by the fandom and it doesn't help the actor is a good-looking guy and good actor. He does get better though.
Peter has this invoked, twice he does something really bad to two girls (filming Emma's best friend's naked breasts while she's intoxicated and getting Darcy in a situation where a sexual predator comes to her house) and they both end up dating him. He too gets better.
Khal Drogo is shockingly popular and beloved. Despite being quite badass, people seem to love his speech where he brags about killing people, raping women and selling their kids into slavery. He is not bluffing either. He also obliterated a peaceful people and didn't much care if the women were raped until his wife objected. And let's not forget that in the first episode, he raped Daenerys just moments after their wedding; yet, and oddly enough, they are made to love each other as the series goes on... A lot of people seem to make him a saint rather than the brutal bastard he is.
Sansa Stark has this sentiment towards Prince Joffrey Baratheon in-universe in Season 1, refusing to see him for the bully and Dirty Coward he is because she is in love with him... until he gets crowned king and orders her father's execution on false charges of treason and makes her watch, and then states he's going to rape her once she starts menstruating, and then also has her beaten when her eldest brother Robb causes Joffrey's armies no end of grief. She is summarily broken of this illusion.
A lot of characters go through this in contrast to their book counterparts, such as the Tyrells and Renly. In the books Renly is a vain and greedy but charismatic guy who comes across as a deconstruction of The Good King, being clearly a usurper who hides his villainy behind a constantly amiable personality but doesn't show any real ruling skills. The Tyrells also look amiable and give out food to end the starvation in King's Landing, but in the books it is pointed out they began the starvation to help Renly's attempt to usurp the Iron Throne. This has proved controversial, as it takes away a lot of the moral ambiguity in the books and turns characters who were basically Villains with Good Publicity into straight heroic examples.
On the flip side, Stannis gets a lot of respect from the fans that the writers seem determined to avert. A lot of it comes from his Adaptational Villainy compared to the books, as well as the fact that he does have a better claim to the throne than most other contenders, which causes a lot of hostility to the idea of Stannis being the uncharismatic zealot that the show treats him as. Based on most interviews with the writers, the idea of him being nicknamed "Stannis the Mannis" seems to have been entirely unintentional.
Euron Greyjoy. Despite being introduced in Season 6 as a Trumpian figure who cut out his crew's tongues and killed his brother (who was admittedly a colossal jerk), he earned this trope in Season 7. His vulgar wit, combined with his appearance of crashing down onto his niece Yara's ship riding a corvus, has made him a fan favorite.
Dr. Gregory Housedoes have a decent Freudian Excuse and is a genuinely skilled doctor. But people go to insane lengths to excuse the crap he's put his subordinates and friends through, and portray the others as horrible jerks to poor little saint House. In example, when Cuddy broke up with him for apparently good, House completely trashed her living room... and people blamed Cuddy for it!
Oh, House did worse than merely trash Cuddy's living room - he drove his car into it. Cuddy and several other people, including her toddler daughter, had been sitting in that room moments before. From his vantage point, House really couldn't be sure no one was still in the room, and for all he knew someone might have walked back in at a fatal moment. It's pure luck he didn't kill Cuddy, her child, or one of the others.
Rather disturbingly Morgan from Camelot. There was even a post on IMDb claiming that Arthur deserved everything Morgan did to him. Well Arthur is a bit of a skirt chaser and slept with a woman on her wedding day (to another man) but Morgan has murdered innocent people, plotted against her brother, raped two men (including her own brother), manipulated her own citizens and imprisoned her stepmother while she walked around pretending to be her. Fan Dumb indeed.
The most famous of soap opera romances, Luke and Laura, began with Luke raping Laura. But the fans liked him.
Find one mobster who isn't adored by fans, and also by the characters. Sonny Corinthos came to town 20 years ago as a sleazy nightclub owner who very quickly lured young and naive Karen Wexler into working as a stripper, ultimately seducing her and getting her addicted to amphetamines—a watered down version of him being a pimp and her being a prostitute, right down to him threatening to kill her when she finally found the nerve to walk away. Jason Morgan treated all of his loved ones like garbage—his behavior toward his girlfriend bordered on abuse, ultimately shunning very trace of his old life (in all fairness, he didn't remember any of it) to become Sonny's errand boy/hitman/partner. Yet they both have a HUGE following, and their fans often ignore their crimes. Anyone who doesn't like them is often vilified. In the past, the writing team also contributed by writing the mob as heroes, and the people who oppose the mob as the ones in the wrong.
An In-Universe example: In the episode "The Stinsons", it's revealed that Barney apparently does this for every movie he watches. For example, he thinks Johnny Lawrence was the titular Karate Kid, thought Hans Gruber was the star of Die Hard(because he was "the only character in the movie in a suit" and "he died hard") and thought the Terminator was the protagonist of his film, even going so far as to cry when he was crushed in the hydraulic press ("they didn't even try to help him!"). Barney's views on the villain being the main character has even extended to outright horrifying villains with little to no sympathetic or redeeming qualities such as King JoffreyBaratheon and Emperor Sheev Palpatine. He even considers the former the wisest and most enlightened king Westeros ever had!
Barney himself is this: By no means is he a villain, or even a straight Comedic Sociopath, since he is genuinely very sweet sometimes, loves his friends and has gone to insane lengths for them, and has gotten lots of character development over the course of the show. But his fans treat him like a saint, with many males thinking that his "awesome" qualities, which in the show are treated in a ridiculous, ironic way that would be pathetic if they weren't so ballsy they Cross the Line Twice, are actually awesome, and many females thinking that he's actually just a sad, lonely, tormented soul who's mentally messed up from his horrible childhood. While the latter actually is true, it doesn't stop the fact that he's also a lying, misogynistic womanizer, an insensitive, selfish jerk, and an unapologetic Manipulative Bastard who almost never shows a conscience and is heavily dependent on Ted as a Morality Chain while at the same time being a Poisonous Friend with hints of Crazy Jealous Guy towards him. However, fanfics have gone so far as to portray his friends as being in the wrong for making disparaging remarks about his more assholish actions or daring to judge him for them.
American Horror Story: Murder House's Tate Langdon. He's an Ax-Crazy school shooter, who also murdered the last inhabitants of the house and impregnated his girlfriend's mother while impersonating her husband, but he's also attractive, portrayed fairly sympathetically, and a passionately protective boyfriend to Violet. Fangirls tend to swoon over the latter qualities and forgive his crimes, portraying him as redeemed by love or as a misunderstood and troubled soul who did everything he did to try to help others.
Arnold Rimmer in Red Dwarf gets some of this treatment. He's thoroughly unlikeable, slimy, cowardly, arrogant, self-pitying and weaselly — and yet, if the show could be said to have a sex symbol, it's him. This is helped by his rather Woobie-ish backstory (even though the series often takes pains to point out that he is at least a Jerkass Woobie, with the 'Jerkass' part firmly emphasized) and some scenes in series 5 involving the actor with his shirt off, which makes it a bit easier for those inclined to downplay the fact that he spends 99% of the series acting like an insufferable asshole. It also helps that in another timeline, he's The Ace, meaning that deep down he's got the potential to be a decent person and a great one. However, this means it also tends to be forgotten that merely possessing the potential for greatness and decency does not automatically make one great or decent.
Also, Ace Rimmer is used by the show writers to prove that Arnold Rimmer is definitely the source of his own flaws. Ace Rimmer had Arnold's life mostly, but not being let off the hook for something at a time when Arnold was is what made Ace seek to better himself.
Regina Mills from Once Upon a Time was a perfect example of the trope in the first season, however the character has progressed in later seasons with a HeelFaceTurn. Regina once got the Leather Pants treatment for these reasons: 1) she's played by the beautiful and talented Lana Parrilla, 2) the character is given a Dark and Troubled Past: being repeatedly abused by her controlling mother, and her father not coming to her defense, having her lover killed by her mother right in front of her eyes, and having to marry into the family of the girl who is sort of responsible for having her lover killed, 3) she is portrayed sympathetically, and, 4) because of the show's once oft repeated phrase and theme: "Evil isn't born, it's made".
Rumpelstiltskin/Mr. Gold is another fan favorite who also gets this treatment. Rumpelstiltskin/Mr. Gold is (literally) a baby-snatcher, a skilled manipulator, has killed people, and, according to Henry, is actually worse than Regina, but that doesn't stop him from gaining a huge fanbase, and certainly doesn't put a stop to him gaining a buttload of apologists who give him a break for his deeds, but crucify other characters for less.
Again, a massively sympatheticbackstory - being born the son of a coward, being forced to fight in a war, crippling himself to avoid a prophecy saying he'd die in battle and leave his son fatherless, spending his entire pre-Dark One life being abused by his entire village as the reviled town coward, finally turning to magic to try to keep his son from being taken away to fight in the same war, being tricked into assuming the mantle of the Dark One, and then losing his son anyways - goes a long way to explaining the Fan Dumb. So does his undeniably genuine love for Belle, as his interactions with her prove that he is capable of acting unselfishly and putting someone he loves above himself.
Jefferson aka the Mad Hatter is another character who gets this treatment, thanks to him having a sympathetic backstory, being played by Sebastian Stan, and knowing how to dress to the nines. The fact that Jefferson kidnapped Mary Margaret, held her against her will, and then drugged and tied up Emma goes ignored by certain fans. Usually in favor of shipping him with Emma. Worse, Emma even gets bashed for knocking him out with a telescope for the sake of escaping with her life and not believing him. Because what sane woman would resist a hot guy who kidnaps and drugs her and puts a gun to her head and not believe a word he says?
Season 2 brings us Killian Jones, aka Captain Hook, who gets excused of a lot by virtue of being played by the extremely attractive Colin O'Donoghue. His most egregious offense to date is removing the heart of Princess Aurora while she was unconscious and promptly handing it over to the Big Bad, Regina's mom Cora. Then, in the following episode, he coldcocked Belle (who was already locked up in a cell) after she refused to help him, and would've killed her had Regina not walked in. While some make the argument that he's a victim of Love Makes You Evil, there remains the fact that the woman he loved and lost was someone else's wife, and that regardless of whether or not he's a villain (he is), violence against anyone (not just women) should be rightly called out as not cool no matter what the reasoning behind it is.
While he's portrayed as performing a Heel–Face Turn as of season 4, he has yet to express remorse for any of this. That being said, he does genuinely care for Emma. and he does regret hurting Ariel.
He actually has a surprising moment of self-awareness in season 5 when he acknowledges that Rumplestiltskin wasn't a monster until he (Hook) got through with him.
Sebastian Smythe from Glee. He stalked Blaine, bullied and teased Kurt and generally was a menace to everyone for weeks, yet people still love to ship him with Blaine, Kurt, or both. Fanfiction with Seb in them tend to portray him as a slightly arrogant Deadpan Snarker and leave it at that. Forget the fact that he almost destroyed Blaine's eye with a slushie full of rock salt or that he turned all of Kurt and Blaine's Dalton friends against them for no discernible reason.
Both Santana and Karofsky, who are bullies, get treated as repressed gays, ignoring some of the awful things that they did. At least with Karofsky they manage to craft a storyline of redemption, where the character recognizes all the wrong things he's done and apologizes sincerely, not to mention tries to make amends by participating in his beard's Anti-Bullying Watch... but go tell that to his fans, who take the Jerk Ass out of Jerk Ass Woobie and run away with it.
It's easy to forget at this point, but Puck started out on Glee as a straightforward bully who harassed the Glee Clubbers and knocked up his best friend's girlfriend, and dude only really completed his Heel–Face Turn in the second half of the first season. He had fangirls all over him long before any of that happened, though.
From the BBC series Sherlock, James Moriarty. He orchestrated an explosion that killed an old, blind woman and several others; kidnapped and threatened to kill three other people, including a child; fed poisoned candy to two children; "sponsored" a serial killer merely to test Sherlock's mettle; threatened to blow up John and shoot Sherlock; and, as of the season 2 finale, has single-handedly ruined Sherlock's career, relationships, and credibility amongst the public. He is a "consulting criminal" who has aided scores of thieves, smugglers, blackmailers, foreign spies and murderers, thus being directly or indirectly responsible for many of the worst crimes in Britain - and likely most of Europe as well. At the beginning of the first episode of the second season, he threatens to make shoes out of freshly-removed human skin; and most viewers have no trouble believing him capable of it. Still, he's intelligent, relatively-harmless looking, and reasonably attractive, and the fandom will ship him with anyone: Sherlock, John, poor Molly (though there is some in-canon justification for that), Mycroft, Irene, and especially his right-hand man Sebastian Moran from the original ACD stories, who has yet to even appear in the BBC version.
Fangirls give a number of villains the Leather Pants treatment. Lucifer is probably the least deserving character who has earned this treatment, but Crowley, Balthazar, and Gabriel have done a lot of sociopathic things.
Lately, Evil!Castiel has been getting this treatment, as has Dick Roman for some reason. Dick is probably even less deserving of leather pants than Lucifer. His name even tells you how much of a horrible person he is!
Amy Pond, the Kitsune from "The Girl Next Door" murdered at least four people and lied to the heroes. Some fans tend to overlook this due to the fact that she was a Girl of the Week for Sam, specifically targeted Asshole Victims, and had a sympathetic motive (she needed live brains to cure her sick son) for doing so. The fact that she was played by Jewel Staite probably didn't hurt, either. So when Dean killed her, much debate ensued both in-universe and amongst the fandom as to whether he had done the right thing or not. After much angst, the show decided that he did, but the subject remains a sore spot for the fandom to this day. However, in Real Life, a mother who had done what Amy did for the same reasons would not be let off the hook for it.
Tony DiNozzo from NCIS. He's a good person deep down, loves and sees the team like family, and isn't by no definition, an actual villain, but his bewilderingly unreasonable fans have no problem excusing and blindly accepting him borderline sexually harassing female coworkers and other women, being nosy as all hell and going through his teammates' possessions and eating their food, bullying McGee in the earlier seasons and just behaving like an all around cocky, obnoxious, and condescending jerk, because of his dysfunctional childhood and daddy issues, his good looks, and sense of humor. But oh, watch them foam at the mouth and unleash hell when other characters (especially McGee or Ziva) give him a dose of his own medicine or say something "mean" to him.
Fitzgerald "Fitz" Grant from Scandal. No matter what he does to his self-professed true love, Olivia, his wife Mellie, or any other character, many fangirls will band together and be united in their cause to defend him, wave off his actions as forgivable because he is such as a sad, repressed, and confused man who just wants to be with the love of his life, but Life and other people just keep getting in his way.
Cold Case has oneshot villains Cameron Coulter and Neal Hanlon, because apparently getting picked on and working dead-end jobs at the mall justifies messily slaughtering everyone there whether they were involved or not, including children.
Jay from The Inbetweeners is more often than not seen as a Jerk with a Heart of Gold and Woobie by the fans, though in the actual series, he is usually a full-blown Jerkass (with a very few Pet the Dog moments). He is also a compulsive liar and a coward. However, his selfishness and especially lies are so over-the-top and Played for Laughs that you will be more busy laughing at him than hating him, which may be why he has become this trope (and the fact that he is at least more amiable than the series' main "villain", Donovan). The woobie thing comes from how he may have a Freudian Excuse: That his father is constantly picking on him. But we don't know if he started to act unbearably and attention-whoreishly because his dad treats him like that, or if he has always been like that and his dad just tries to bring him down to earth. At any rate, Jay is amusing, but he isn't a guy most people would want to hang out with in Real Life.
An in-universe example on Frasier. Martin and the boys talk about Hester as if she were a saint, but from what we know about her: She cheated on Martin at least once, she egged on the rivalry between Frasier and Niles that continues to affect them in adulthood and that's not even counting her manipulative, shrewish behavior on Cheers. On the other hand, they wouldn't exactly be the first grieving sons/husbands to ever decide to Never Speak Ill of the Dead when it comes to a deceased and clearly much-loved-and-loving-despite-her-flaws mother/wife, so this is perhaps understandable.
Damon Salvatore from The Vampire Diaries has a very vocal fanbase despite the fact that he is a rapist, serial killer and unapologetic jerk.
Klaus Mikaelson fits the bill as well.
With this show, it helps that after a while no one's hands are clean, so your favorite characters are less about any kind of morality than who's more fun to watch.