Damian Wayne was this for a while. At first fans couldn't stand his snide attitude, the massive amounts of lenience that he seemed to get for things that some fans found unforgivablenote beating up Tim Drake, and beheading a D-List villain to name a few but Grant Morrison kept using him in his stories. When he eventually became the Robin to Dick Grayson's Batman, many fans complained, but he mostly won naysayers over with him as the "dark, snarky" Robin that Jason Todd failed to be during his tenure (helped greatly by a massive amount of Character Development). Now, with his long-delayed death finally occurring, more fans are begging for him back than cheering with joy. He's still considered a Creator's Pet in the animated films, however.
Jason Todd as well, and for many of the same reasons. His characterisation since coming back from the dead changes depending on the writer, which makes it seem like DC is throwing it all at the wall to see what sticks. The attempt at darkening him has him do things that no other Bat-character could get away with, such as casually killing (emphasis on the casual) and using guns (Peter Tomasi did however write him as going for leg shots in front of Batman), while having the negative personality aspects of Damian, but none of the charm, nor the excuse of being a child. The fact that he's been written by disliked writer Scott Lobdell for so long has fans begging for anyone new to take over.
Harper Row. She was created because of the post-New 52 veto on Cassandra Cain and Stephanie Brown, but since they've come back she's been shilled as basically better than either of them as well as the 'uber Robin'. This includes things like being more determined than Steph (who's famously the biggest Determinator in the franchise in terms of never quitting despite horrible odds) and central to every part of Cass' character development to the point where her whole motivation is now based on Harper. We're frequently told how great she is without any evidence and nobody ever calls her out on any of her frequent Jerkass-ness. And she's also an uber tech genius that surpasses Tim Drake (the tech guy in the Bat-fam) somehow despite debuting with basic skills based on electronics. Oh, and she becomes an Instant Expert and is able to pull of advanced acrobatics and fighting despite barely being trained. Even in Detective Comics (Rebirth), a series that's basically the Batman Ensemble Darkhorses in a team book, Harper got more focus than Cassandra Cain for the first two story arcs, and Harper's not even in the main cast.
There's also the amount of focus she gets. Batman Eternal and Batman and Robin Eternal were both advertised to feature the return of Stephanie Brown and Cassandra Cain, respectively (the second was also about the Robins). While they do get their origins and appear, Harper also gets extensive focus, even overshadowing the two in many people's eyes. It's basically advertising that your comic will feature the return of a fan-favourite character... and it does, but more heavily features your own original character that people don't like.
Earth 2 has a Pet quartet: Val-Zod, Thomas Wayne, Red Tornado Lois, and Jimmy Olsen. Though they were introduced in the well-liked Robinson run, it was under the pen of Tom Taylor that they became outright hated. The entire premise of the book was that it was a world where the Trinity were Killed Off for Real and the book would instead focus on the ex-JSA Ensemble Darkhorses, so bringing in Suspiciously Similar Substitutes to the two most overexposed members of the Trinity and their supporting cast went over like a lead balloon. And that's before they started grabbing character focus and arcs like crazy, even taking a disproportionate amount of cover space, while the original main characters were weakened, Demoted to Extra, or just plain forgotten. The result was one of the most unique books in DC's library at the time being reduced in the eyes of readers to a second-rate knockoff of Injustice: Gods Among Us, with an appropriate crater in the sales. Fans consider them incredibly boring and completely redundant, and often theorize that Taylor is being ordered by editorial mandate to use more recognizable characters (which would explain why Robinson quit). Things might change for the new Earth-2 book following Convergence, where Thomas Wayne is now dead, and emphasis will hopefully be more on other characters like Jay Garrick or Alan Scott.
The Flash has Barry Allen, the second Flash. Barry pulled a Heroic Sacrifice in Crisis on Infinite Earths (a crossover from the 1980s) and this led to his sidekick, Wally West, taking up the mantle of the Flash. Fast forward to the late 2000s, and people who grew up with Barry are Running the Asylum, including Geoff Johns, who has actually said that Barry is a favourite character. So, Barry returns and succeeds Wally in being the protagonist of the Flash ongoing. Then Flashpoint happens, and Wally is rebooted out of existence, along with his wife and children, and Barry is established as being the only Flash.
Even in Justice League: Doom, an animated adaption of a JLA storyline wherein the Flash was Wally, the Flash is Barry. The plot would be no different if the Flash was classic Wally (in contrast to switching Kyle out for Hal, which at least made sense with the villainous counterpart they used).
Between 2011 and 2016, the other Flashes were completely different characters with only a few similarities with their pre-New 52 counterparts, while Barry's character remains mostly intact. That alone speaks volumes about the favoritism to Barry.
Until DC Rebirth, written by Geoff Johns himself, brought Wally back.
Dwayne McDuffie had Green Lantern John Stewart, though this was largely part of self-fulfilling prophecy; a lot of fans didn't like Stewart for the way he leapfrogged Kyle Rayner (previously established in the animated canon) and longtime comic GL Hal Jordan to be the Justice League Unlimited Green Lantern. This led to McDuffie (a black creator who was quite vocal about racism within the TV and comic industry, and who had inherited Stewart on the cartoon from the previous showrunner) making some comments equating hatred of Stewart as racism, which led to the widespread notion that Stewart was McDuffie's pet character. Fast forward a couple of years when McDuffie took over the Justice League of America comic and he was told to use John instead of Hal as the Justice League of America's Green Lantern on orders from above (partly because Hal was being given HIS JLA TEAM!). Sadly for McDuffie, fandom took the change badly, not helped in the least by the fact that Hal's JLA spin-off was delayed and reduced to a mini-series when it became apparent that James Robinson's artist was never going to get the book done on time. This lead to Hal returning to the title until his book was ready, followed by John's reinstatement just long enough for him to be bounced again and replaced with Hal until he was quickly replaced with Jade when they needed a book to focus on her Brightest Day storyline. The entire process was made progressively worse and worse by Executive Meddling, in case you couldn't tell. And when McDuffie had the gall to describe this and the other creative difficulties on his forum (without assigning blame or complaining), DC responded by firing him.
One could argue that the Green Lantern has been a source of shilling the creator's pet since the 90s. Start with Kyle Rayner replacing Hal Jordan and the writers trying to shill him to win over the fan base disgusted by Hal's Face–Heel Turn in Emerald Twilight. Fast forward 10 years, and a number of those fans are now writers/editors for DC, and they promptly retcon the heel turn and restore Hal to being GL Numero Uno - and now must shill him to the fan base who grew up with Kyle and are upset with him getting booted down - and John Stewart as described above.
Interestingly, a few writers did make Kyle work for his place in the DC Universe. A number of writers, like Grant Morrison, had characters like Wally West look down on the rookie Lantern for just being there and made to bust his chops to earn his place in the greater scheme of things.
Geoff Johns' Hal Jordan can come off as this at times. He's the Greatest of Green Lanterns, and constantly told so, even though the bulk of his accomplishments are only achieved through dumb luck; he can be as much a Jerk Ass as Guy Gardner, yet rarely be called on it, because the Parallax fiasco was retconned into being him possessed by a giant bug, that was apparently inhabiting him for years without any real change to his personality until he went nuts; his record is now spotless and he's somehow so important to the Universe that he's been able to sample the entire Emotional Spectrum, just because he's Hal Jordan.
There was a period when Magog, of all characters, was one of these. Originally created by Alex Ross and Mark Waid as a scathing deconstruction of the '90s Anti-Hero archetype for their Kingdom Come book, Magog would find a new lease on life a decade later when he was imported into Justice Society of America by Geoff Johns as part of an effort to focus the book on a new generation of Legacy Character types. At first this introduction seemed quite promising, as the young not-yet-Magog was introduced as a polite and respectful soldier who worked and played well with his teammates. This character would become Magog through the year-long 'Thy Kingdom Come' story arc, during which he was promoted to main character status to play off the story's villain Gog. Fine and dandy. But after that storyline came to a close and Geoff Johns left the book, Magog would remain a main character under new writer Marc Guggenheim (something that did not sit well with many fans who had favorites of their own among the many newly introduced characters, none of which were featured as prominently as Magog). This might have still worked out if the character had remained likable, but under Guggenheim's pen he quickly degenerated into a disagreeable, contrarian Jerk Ass who seemed to delight in pissing off both his teammates and readers. While a small fandom for the character persisted (very small, if the sales of his brief solo series were anything to go by), Magog very quickly acquired a much larger Hatedom, one that was not at all shy about voicing their distaste for the character. DC listened to the complaints, first by having old-school heroes Power Girl and Alan Scott clean Magog's clock, and later killing him off in an almost needlessly gory fashion to placate the fans. Even after nearly a decade the character has not recovered from this damage, and since the New 52 he has been reinvented as an outright villain.
Superboy Prime. Originally an unexpected hero from the original Crisis, he was later grabbed by writers and re-tooled into a brainless, self-entitled brat who went on super-powered temper tantrums against comic heroes for not being who he wanted them to be. Essentially he was a rather mean-spirited Take That!to comic book readers. Naturally, writers didn't seem to like Prime that much, making him a pathetic joke who only seemed to get more and more pitiful every time he showed up, but he was continuously brought back over and over again for major events, despite the fans growing more and more fed up with the joke every appearance. One particularly eye-rolling moment in a Prime story showed us a comic-book shop in the "real world" where the fans were laughing about how "Hilarious" they found the character.
Danny Chase from DC Comics' New Titans was universally loathed by fans within a few issues of his first appearance. He was a Cousin Oliver (he even looked like the original Cousin Oliver) introduced to make the team seem younger, as he was only in his early teens while everyone else was pushing 20. Despite his age, he constantly argued with the other members of the team, criticized them, was supposed to be a genius superspy teenager with telekinetic powers, but then went crazy with fear whenever an actual fight took place. And when Dick was distraught at the death of Jason Todd, Danny said it was no big deal because Jason 'knew the risks'. The only people who didn't seem to grasp how loathed this character was was writer Marv Wolfman who, to this day, still insists it was the readers' fault for not "getting the character," and weirdly enough Linkara, who calls Danny his favorite superhero ever. ("I am NOT kidding at all. I love the little brat.")
As a tip, in a series about costumed superheroes with codenames, whose fans presumably enjoy reading about costumed superheroes with codenames, having a character who continually goes on about how lame costumes and codenames are and how he's too cool for a costume or codename probably isn't going to go down too well.
It also hurt that Marv Wolfman had no idea how to write a telekinetic to complement the Titans' diverse power set. Chase's powers were mainly shown to be (at best) extremely limited: at best he could levitate himself (but only while sitting Indian-style) and throw small objects around at bad guys to annoy them. Jean Grey he wasn't; this combined with his wussy behavior during combat, made him practically useless in battle. As bad as Cypher was power-wise, at least he had training in hand-to-hand combat and was willing to take a bullet for his teammates when necessary.
Deathstroke was also Wolfman's Creator's Pet for most of his run. When George Perez left The New Teen Titans, Wolfman had free reign over Deathstroke's character, and it seemed that he had no objectivity where he was concerned. In a very jarring, sudden turn of events, Deathstroke became a Karma Houdini for his actions, his earlier characterization forgotten and now established as an Anti-Villain who bore the Titans no ill willnote (When Perez was still on the title, Deathstroke blamed the Titans for his son's death and took very clear, visible pleasure in setting them up to be betrayed and murdered) turned Anti-Hero, being Easily Forgiven and becoming a father-figure and friend of the Titans, including his biggest victims Nightwing, Changeling, and his own son Jericho who was rendered mute because of him. Wolfman has also stated repeatedly that he never saw Deathstroke as a villain, but as a victim of circumstance stuck in a bad situation, whose actions (including sleeping with a teenage girl) weren't truly his fault.
He was Brad Meltzer's Creator's Pet as well, although ironically Meltzer went in the opposite direction from Wolfman. Instead of attempting to canonly apply the Draco in Leather Pants treatment to him, Meltzer made Deathstroke an unabashed villain who was just so good at what he did, being both an invincible fighter and unparalleled Diabolical Mastermind. This was best shown in the notorious scene of Identity Crisis where Deathstroke singlehandedly curb-stomps the entire Justice League. Meltzer was clearly a tad too enamored with Deathstroke as a villain.
The second Wonder Girl, Cassie Sandsmark, was felt to be this after she became team leader in Teen Titans volume 3. While talked up as a leader by the writers, Cassie didn't really do all that much and more page time was often given to her acting obnoxiously condescending or being a Jerkass to her boyfriend. Fans also felt insulted when Felicia Henderson brought Beast Boy back to the team: Rather than give him his leader role back, Henderson had Cassie continue to be leader while lacking any character development, while the older and more experienced Gar was demoted to obnoxious comic relief and treated as if he were younger.
Avengers Arena had several, most of them original characters. The biggest one is probably Apex. She is supposed to be one of the smartest people on the Murderworld, but she was only successful because everybody she went against grabbed an Idiot Ball much bigger than the one she carries around, and because stronger characters were subjected to The Worf Effect to make her look cooler, especially Darkhawk - she can effortlessly take control over his armor and even break its bond with the host. When her plan from the first arc blew up in her face, it's treated as a big accomplishment by the other side, literally being said to be beating her at her own game, despite the fact she made many stupid mistakes that lead to her failure - many people see it as Character Shilling. Many plot points ends up revolving about her, even if they shouldn't, like the broken trust between Chase and Nico. In the second arc, she kills Juston, takes control over the Sentinel, Deathlocket, and Darkhawk and uses them to effortlessly curbstomp X-23 and Nico Minoru, effectively dominating every established character who could be seen as a threat, and is only defeated thanks to a writer-breaking rules under which Nico's magic work to give one of them necessary powerup to fight her off. Also, Deathlocket, one of series initial Ensemble Darkhorses has been turned into Satellite Character, who only exists to make Apex look that much more interesting. Apex is also the only character to get more than one focus issue: #9, which tells her origin, and #12, which is told from her perspective, while some established characters (like Mettle, Red Raven and Juston) didn't get a single one before they died. Critics of the series started calling her Neelix to express how annoying she is.
Cammi is another one - while nobody denies she is an experienced survivalist and badass, she is also set up as an unquestionable team leader in the second arc and other characters, including those who actually are experienced leaders (Nico Minoru, Reptil), follow her without a question and even ask what they should do in situations which they should be better suited to handle in the first place. And worst of all, she keeps this position despite making stupid decisions and when Cullen finally calls her on it, it's treated as him having an emotional breakdown, not pointing out how an horribly incompetent leader she is.
And she only gets worse in Avengers Undercover. She is the one person damaged the least by Arena and the unquestionable leader of the group, the only one to oppose idea of killing Arcade, the only one whose family and friends doesn't seem to turn on when they get arrested after one of them kills him, and the only one to refuse Baron Zemo's offer and the plan of taking down the Masters of Evil from inside, because she wants to stay morally pure. She goes on to play Author Avatar when she says how "people've been hating us for six months now, so I don't care how much more hate I get" (it should be noted that only 3 months passed in-universe and Arena survivors were supposedly seen as celebrities, so it's clear the jab at the hatedom). When she tries to leave, effectively abandoning her supposed friends in the hands of the villains, it's supposed to be seen as the right decision, and when she is attacked by Constrictor, it's supposed to be a dramatic moment (when in fact most of people either laughed or ground their teeth at Constrictor's Character Derailment). And of course in the finale she steals Arcade's godmode-technology and single-handedly defeats Zemo and Masters of Evil, solves everything, and flies off to space, like if somebody realized she turned into a Poochie.
Other Braddock Academy kids, especially Cullen Bloodstone and Anachronism, are this to a certain point as well, because, with the exception of Cammi, other characters rarely get a chance to show any initiative and are constantly Demoted to Extra and subjected to the Worf Effect to make them look better.
Anachronism got worse in Undercover, where suddenly he is hailed as great leader material and Hazmat suddenly gets over her dead boyfriend and falls for him out of nowhere. Made worse by the fact many consider him to be Dennis Hopeless's self-insert.
And of course Arcade is one too, being portrayed as a genius who managed to outsmart everybody in the Marvel Universe to have his sick game run for a month without anybody noticing, when in reality his plan worked only because everybody who could stop him had either been handed the Idiot Ball or been written as uncaring jerks. We're supposed to see him as a clever mastermind who manipulated the cast into fighting each other to death for his amusement, when in reality he needs to make one ham-fisted interference after another to try make the kids play his game, clearly showing he didn't think his plan through. Furthermore, with three exceptions, two of which don't really count anyway (Apex, who was already playing without his push, and X-23, whom he can get to play if he sprays everybody with Trigger Scent, that sets her into state of uncontrollable rage, which cannot be counted as playing on her own will), all of them failed. In the last arc, when everybody starts fighting each other, Arcade claims he broke the kids, and we're supposed to see him as right. There's only one that has been lead naturally to the point where he has understandable reasons to try to kill somebody else (Aiden trying to avenge Nara). Others not only don't have one, but one of them (Nico Minoru) experienced things that make her suddenly trying to kill others make no sense whatsoever (she died and came back to life to save the same people she now suddenly tries to kill) - it comes out as Character Derailment for the sake of validating Arcade's claims. It also happens after Arcade rants in defense of making the game last thirty days, which looks like Dennis Hopeless putting words in his mouth in defense of a commonly criticized plot point.
And he too gets worse in Undercover - suddenly the whole world loves watching the videos of Murderworld he put on Youtube, and a single of them has more views than everything most popular Youtubers did combined, despite the fact that a) they would be instantly pulled down for violating Youtube terms of service and b) they are videos of kids being killed. Arcade is hailed by media as some underestimated genius and the kids who survived it are seen as celebrities. Nico gets even chewed by Chase for daring to be traumatized by Arena - she should accept Arcade won and enjoy the fame. When the kids supposedly kill him, it's seen as first-degree murder by SHIELD and their friends and family immediately turn on them. And in the end he gets away with everything again - not even being killed, just losing his godmode powers. Even Baron Zemo, fan-favorite villain, says he disapproves what Arcade did, but still goes on a page-long series of praises to him.
Roger Stern really liked Monica Rambeau, the Captain Marvel of The Avengers, and actively pushed her into the limelight. He repeatedly had other characters talk about how powerful she was, men gushed over her beauty, and she was even made chairman of the Avengers for a time. The fans never quite took to her, but she was never really hated. She did develop a larger fanbase once Warren Ellis made her a member of the Nextwave series.
Kate Bishop in Hawkeye normally isn't this, being given plenty of panel time while not overshadowing Hawkeye, her mentor and the main protagonist. However during Jeff Lemire's run on the book during All-New, All-Different Marvel, she seemed to be suddenly suck up loads of attention and was shilled massively, being depicted as much better at fighting than Hawkeye to the point that a villain at one point calls her "the real Hawkeye" for no particular reason. This may have been an attempt to reverse Badass Decay Kate suffered in the previous writer's run, but if so many fans feel that Lemire went way overboard.
The Red Hulk under Jeph Loeb, dear Lord... shortly after being introduced he beat odin-forced Thor with his own hammer, punched out the Watcher, killed the Grandmaster (who is immortal), casually killed off the whole Defenders (including the Silver Surfer!) and much more. Luckily, he got depowered when Parker took over, and every hero that has been beaten by him before returned to return the favor in some very satisfying ways.
The Good News: He's finally dead! The Bad News: Despite being utterly useless for most of his comics existence and a Face–Heel Turn that also revealed he was an Eldritch Abomination and saw him try to destroy the world his send-off issue was nothing but the entire cast of Marvelverse heroes waxing poetic about how wonderful he was and how he'd made their lives better in flashback retcons. The hamfisted attempt at Alas, Poor Scrappy was not well-received. The Worse News: He got revived by The Apocalypse Twins and is out in space only doing God knows what.
He's also an example of a God-Mode Sue. He's better at molecular manipulation than Molecule Man, for instance (it is debatable as to whether this was the Sentry or the Void, an issue even further complicated by the fact that no one really knows what the hell either of them are). All this may come with the territory, given that he's heavily implied to be Death and all that...
He's a perfect example of an interesting character/idea turned into a walking plot device.
Introduced at the start of the "Brand New Day" reboot, she was quickly established as being Peter Parker's next love interest. Initially she started off as a minor character who just happened to have a crush on Peter, but recently writers have been cranking it up how much she's perfect for Peter, having both Peter complain about not being worthy of her and Mary Jane telling him he needs to hook up with her. Oh, and did we mention she's named after Joe Quesada's daughter?
Also, she's coming off as a Composite Character to many. Tries hard to invoke the Nerds Are Sexy trope, presumably so that she's "on the same intellectual level" as Peter or some such nonsense? Deb Whitman. Has a tragic past involving her father (really, couldn't even make it the mother? Or another authority figure?), that really doesn't come off as being as bad as MJ's was. Touted as being the "perfect girl" for Peter, being idolized (this time by people in-universe, as opposed to in fans' memories) Gwen Stacy (fans hope she will complete this set by dying) Falling in love with "plain" ol' Peter Parker?Mary Jane again.
However, there's a light at the end of the tunnel: the recent Spider-Island storyline ends with Carlie breaking up with Peter precisely because he didn't tell her he was Spider-Man, while Mary Jane gets closer to Peter. The comic also focuses on Carlie's negative traits and MJ's positive ones: when people in New York start developing Spidey's powers, Carlie uses hers to play around while MJ helps Peter and the Avengers fight the Big Bad.
Unfortunately, she's still not going anywhere anytime soon. Despite having had broken up with Peter, Carlie is still sticking around in the book. In addition, she's starting to pop up in other books like the Punisher. Not only won't she go away, she's being featured in more titles despite an utter lack of enthusiasm on the part of the readers. And if you were thinking that she'd be portrayed in a negative light, the creators insist that she - out of anyone else in the books - is perhaps the "sanest" member of the cast.
Oh, and let's not forget, in Superior Spider-Man, she is the first person to figure out that Peter is obviously acting incredibly out of character and decides to investigate. Not Mary Jane, the love of his life. Not Aunt May, the woman who raised him. Not even the freaking Avengers, who have fought side by side with him for years! This woman is the one who figures it out, in the most simple way possible. You want to know how? She follows Spidey's money trail that he's using to pay for his minions and gear, and it belongs to Otto Octavius. The main character, who many criticize for being a Villain Sue, made that stupid a mistake, and yet nobody figures it out but Carlie. Even worse, when she gets hit a dose of the Goblin formula, she's the only one who can resist its brainwashing powers. At least she maintains noticeable scars on her eyes after she gets cured.
Finally, she was one of the "great loves of Peter's life" in a special one shot - despite not having appeared yet in a single comic. Go figure.
Many detractors towards Dan Slott tend to paint his usage of Spider-Man villain Doctor Octopus as this, especially after he became the Superior Spider-Man. A major complaint by fans toward this end is that Otto's thus-far-successful attempt at hijacking Peter Parker's life has less to do with him being clever and strategic, and more with all of Peter Parker's friends, allies, and family becoming total, brain-dead idiots, with the plot at times bending over backwards to keep Otto from getting egg on his face.
This seems to be a running trend with Dan Slott and Spider-Man characters. Peter's newest love interest Silk has had even less of a relationship with him than Carlie had, being clumsily shoehorned into Peter's backstory during the Original Sin event. From there she essentially hooked up with him on the spot, thanks to having Spider-Man focused daterape powers, showcased having superior powers to Spider-Man and somehow being just as skilled as him despite utterly lacking in training, experience or education. Since her debut she has been RELENTLESSLY shilled as a love interest and hero without any sign of irony or self-awareness from the writer's part. Part of this shilling was Slott going out of his way to destroy Peter's relationships with his other potential love interests, such as having Mary Jane and Carlie abandon Peter and New York altogether with an incredibly flimsy justification, and turning Black Cat into an Ax-Crazy terrorist whose motivations and reasoning for going fully evil make absolutely no sense. Dan Slott has even gone on record to say that Silk was responsible for the sales of Amazing Spider-Man (a comic that normally gets high sales, and was obviously benefitting from the fact that it was a relaunched series that debuted alongside Amazing Spider-Man 2) and that he has received a high amount of fan mail praising her yet refuses to post any evidence to that fact when asked for proof.
The crowning achievement of her hate would have to be Spider-Verse, where she still got pushed despite having little to nothing to do with the core concept, taking time away from the alternate Spider-Menthat the story is supposed to be about. In a story that's supposed to be about Spider-Man's history, effective newcomers Silk and SpOck (see above) are the ones who the entire plot hinges on, doing most of the important things and getting heavily pushed as major characters. Meanwhile, Ensemble Darkhorses like Scarlet Spider, Spider-Girl, the Japanese Spider-Man, and many others are shoved into the background, subject to the Worf Effect, or unceremoniously killed off.
Thanos of Titan and Adam Warlock have fans, but readers find Thanos' continual presence at the center of crisis crossovers annoying, along with the fact Jim Starlin will delete or handwave less glamorous showings of his pet Thanos, unless the reason for them was his other pet Adam Warlock. This is also part of the reason Squirrel Girl has fans because she was part of a gag that parodied Thanos' uber-competence and the tendency for his screw-ups to be explained away as inferior clones or part of his plan.
Many of Thanos' fans like him for being a vile villain, but don't like the attempts to make him seem sympathetic despite hardly doing anything sympathetic ever. He routinely kills billions of people and not just in A Million Is a Statistic ways but takes much joy in causing as much suffering as he can individual to individual. We're supposed to feel bad because he's in love with the personification of death and was rejected when she realized he was no good.
Most Thanos fans enjoy Thanos not from his original appearances, but from the 90s, when he was a Deadpan Snarker and someone who sought to save the universe not because it was the right thing to do, but because Thanos pissed off Death and doesn't want to even contemplate what would happen to him if the universe was destroyed since Death won't let him into the afterlife. This created a bit of irony of sorts, as Thanos received a great deal of character development from Starlin in the 90s at the expense of Adam Warlock in terms of Warlock being reduced to Thanos' emo sidekick.
Kitty Pryde became Peter Parker's girlfriend in Ultimate Spider-Man and, after they broke up, remained a part of the cast and was fit into as many plotlines as possible. Brian Michael Bendis has gone on the record to state that he's always liked Kitty Pryde from back when he was a kid and that he enjoys using her... combine that with a statement he made about Peter "being him" and the conclusion to come to is pretty easy. Some don't mind the attention paid to her... but others do.
Then there's Bendis adding the main version of Kitty Pryde to Guardians of the Galaxy, of all comics, having her date Star-Lord and rapidly become engaged to him. She's now scheduled to become the new Star-Lord ("Star-Lady") and take Peter Quill's place on the Guardians.
Some characters in his Avengers comics - Spider-Woman, Luke Cage, Jessica Jones and Ares - are accused of being Creator's Pets. There is some balance though, because Bendis has a tendency to showing his affection by heartlessly breaking them, so all five went through some serious crap under his care. But for many fans it's still not enough to equal all the attention he gives them. And that's not counting Bendis' "love" for Hawkeye, who has become nothing more than a vehicle from which Bendis attacks his critics (and to spite fans whose overwhelming hatred for Bendis' attempt to permanently kill Clint off led to Bendis being forced against his will to bring him back to life, at which point he turned him into a ninja to further spite fans).
Luke and Jessica have gotten additional flack from fans for the opening arc of The Pulse, where they're the ones who did most of the work in exposing Norman Osborn to be the Green Goblin following his post-Clone SagaVillain with Good Publicity status, with said fans thinking that if anyone should've exposed Spider-Man's archenemy, it should've been Peter Parker himself.
Nurse Annie Ghazikhanian in Uncanny X-Men. Universally maligned "writer" Chuck Austen introduced the single mother/apparent expert in mutant physiology shortly into his equally despised run on X-Men. Word of God stated she was based on Austen's real-life wife, never a good start. He quickly made her the inane central character in many of his story lines. This usually included:
Vapidly gossiping about sexy men with once-intelligent characters Husk and Northstar.
Throwing tantrums/acting holier than thou during battles and various X-Men crises.
Dispensing shallow advice to other characters on their "romantic woes".
Wrapping bandages around injured characters' heads (regardless of their actual injury)
Apparently getting boned Iceman for no apparent reason.
Annie is mostly remembered for her creepy relationship with Havok, which started as a crush when she was caring for the longtime X-Man whilst he was in a comatose state. Once revived, Alex showed an immediate and unfounded attraction for Annie also. It was eventually revealed Annie's equally creepy mutant son Carter had been setting the two up on 'psychic dates' for months, allowing Austen to place the two characters in a relationship without needing to bother about annoying things such as context or developing a rapport between the characters. To further infuriate and confound readers, Austen also depicted Havok's longtime partner Polaris as an insane, homicidal, bitchy ex to further drive home the point that Annie was The Virgin Mary and Gandhi rolled into one.
Fan reaction to Annie (and Austen's run in general) was overwhelmingly negative, a fact that the writer dismissed as unreasonable "trolls". With his final story arc with the X-Men franchise, Austen wrote Annie and Carter out of the X-Men books. The pre-Austen Polaris/Havok relationship was restored in time and Annie was never mentioned again, presumably dying on the way back to her home planet and/or country.
Quentin Quire of the New X-Men started off as a minor character, basically the super-powered mutant equivalent of a school shooter and a teenaged sociopath who manipulated others into joining a small cult of wannabe Magnetos, before dying of a drug overdose of sorts. He was revived a few times, before finally returning during Schism, serving as one source of the conflict between Wolverine and Cyclops to push them apart further, before joining Wolverine's school. He's continued to be written by Jason Aaron, who's since then made him one of the main characters, including being the main student, of his run, with him being at the front of every big event he writes, including his future self being the Phoenix in Battle of the Atom. All of this, despite being largely loathed by vocal aspects of fandom. Every writer tends to have one kid they push, and usually it works. This case, however, it most certainly has not, and isn't helped by his continued use.
X-23 gets hate for this too. Being a teenage Opposite-Sex Clone of Wolverine, she is everything everyone hates about him, with very few of his redeeming qualities like wisdom and compassion. Instead, she comes across as an antisocial jerk, and yet the writers fight themselves over who puts her in what. Her role in New X-Men in particular, once her creators Craig Kyle and Chris Yost took over the title, you could be forgiven for thinking was written by a thirteen-year-old girl. She's portrayed as having New Powers as the Plot Demands, usually something related to animalistic senses, that enable her to figure things out before anyone else, as well as ten times the competence of the other kids with none of their charm coming with the territory of being inexperienced teenage superheroes. As the final punch to the gut, she hooks up with the hot bad boy character after his original love interest is clumsily written out. And it didn't do her any favors that the original main characters of the series were either unceremoniously killed off, written out or demoted to extra to make room for X-23 being the primary focus. This is ironic, given that she was initially an Ensemble Darkhorse when she originated on X-Men: Evolution. Perhaps it's the fact she has poor characterization these days while being a regular (always a failure of a combination for any character).
For reference, any time Craig Kyle (one of her creators) has done writing for an X-Men-related series, she is a main character. The only exception is his Amazing X-Men, wherein he can't use her, since All-New X-Men, the flagship X-Men book written by Brian Michael Bendis (both of which have priority over Amazing), is already using her and she absolutely cannot appear in Amazing X-Men.
Chris Claremont, while a beloved writer, is quite notorious for this, particularly with female characters. On several different occasions, he has championed the cause of one X-woman or another, often putting them to the forefront, and continually using them on different books. This isn't entirely negative, as many of the women turned into great characters, but started rubbing fans the wrong way when Sage was shoved down fans' throats upon his return to the X-Books. Suddenly this character (who'd only been "Sebastian Shaw's Secretary/Assistant" before this) was everywhere, getting constant cover appearances, saving the day, and becoming central to several stories. Despite no fans really liking her, Claremont used her again and again in subsequent books, as every time he got taken off one series, he'd transplant her to his new one. This got most egregious when the mainstream Sage ended up in Exiles, which almost always used Alternate Universe versions of mainstream characters.
The same thing in regards to Claremont's writing of Psylocke, as he had her placed on the Exiles and had her actually usurp leadership of the team away from Blink, who is a very big Ensemble Darkhorse.
Steve Englehart became notorious for his over-use of the character Mantis in his The Avengers run. She appeared, beat the snot out of all of the Avengers at once, and then immediately became the central character in a huge Myth Arc that took up years of storytelling. Then, when he was out of Marvel, he created a Captain Ersatz for her in DC. Then another company. Then tried to use her again at Marvel. To date, he is the only writer to ever seriously use her as a major character (a few writers have gone on record that they hated the character behind-the-scenes, and didn't see what Englehart saw in her) — her next-biggest appearance is likely as a supporting character in Annihilation: Conquest, followed by being one of the title characters in Guardians of the Galaxy.
He also, weirdly, decided to make her a big focus in his Silver Surfer run. Fan reception was no better there, with Strangled by the Red String occurring as he tried to make readers believe that she was Norrin's true love, when everyone was already hoping he'd get together with Nova... which he eventually did, when Mantis was written out of the series, to the relief of all.
Spider-Gwen in Web Warriors. While in her title, she's shown to be a rookie way out of her league against superhumans, in Web Warriors, writer Mike Costa turns her into The Ace who can handle both armies of Electros and Dr. Octopuses with ease. Spider-Man: Noir ends up describing her as someone who really doesn't need to be part of the team when most of the heroes shown in the series have been fighting for so much longer and dealt with a lot more.
Miles Morales has become infamous for being Bendis' creator's pet. Despite being an new, amateur kid hero, he has the tendency to beat everyone when written by Bendis (which is all the time), including his far more experienced predecessor Peter Parker from the main universe. The worst example was probably Miles defeating the uber powerful Eldritch Abomination Blackheart, just after this one had taken out all the other heroes. This also applies to other characters Bendis creates; both Goldballs and Riri Williams have been pushed heavily outside their own comics and disproportionately praised by other characters.
Orlando becomes this in The League of Extraordinary Gentlemen: Century. Moore pulled a bunch of unrelated obscure characters into a big stew to create Orlando, a character described as "omnisexual" and having slept with absolutely everybody ever, including all the main characters. Moore depicts Orlando as being the best fighter, the wielder of Excalibur, and basically flawless. Note that few of these traits were present in the original works, so Orlando could easily be labelled a Possession Sue. Despite generally being loathed by readers, Orlando features prominently throughout Century, and ends up helping to kill the main villain and surviving to the end, while established characters Allan and Mina (the only survivors of the original cast) get pushed to the side and contribute almost nothing, with the former suffering an insultingly ignominious death.
That said, everyone in the comic eventually realizes Orlando's a colossal Jerk Ass, and both Mina and Allan leave Orlando. It's implied their attractions to Orlando were infatuations to Orlando's novelty, and that the novelty wore off surprisingly quickly offscreen.
The Silent Hill comics had more than their fair share of problems, but worst of all was the addition of Christabella, a Creepy Child who commands an army of monsters and constantly spouts off curse words and wisecracks in a manner befitting Freddy Krueger. Not only does her inclusion run completely contrary to the plot and mood of Silent Hill, but Dead/Alive ends with her give complete control over the town, when most readers would have preferred to see her fed to the Slurper.
At least she was forgotten when Tom Waltz took over the writing chores of the comics.
In the Sonic the Hedgehog comic, a character was introduced named Tommy Turtle, a childhood friend of Sonic that had never been mentioned before, but had once taught him a valuable life lesson. He died in his first appearance while performing a Heroic Sacrifice to save Sonic, but about a year later was revealed to not have actually been killed and was brought back. Unfortunately, after bringing him back, the writers didn't seem to have any real idea what to do with him, and attempts to make him more relevant (such as having him become infested with nanobots, causing him to develop Transformers-esque abilities) ended up just appearing ridiculous and making fans hate him. In Sonic Grams while Archie staff admitted that they knew a lot of their fans hadn't liked the character, they'd hoped they could change their tune, showing the clear divide between the staff at Archie at the time and the people actually reading the book. In the end writer Ian Flynn said when compiling a list of the comic's most unpopular characters, Tommy still ranked very high among the fanbase despite efforts to make him popular by previous writers. Tommy was therefore killed off (performing anotherHeroic Sacrifice) and hasn't been seen since.
Different writers have met criticism over over usage of certain cast members. Ken Penders was noted for his expansion of the Echidna brotherhood, which by the end of his run had its population and story background bloated to a convoluted rate. Later writers preferred to limit their numbers and had numerous Echidna characters Killed Off for Real. Ian Flynn however has been noted for his heavy usage of Sally Acorn, reestablishing her as an active Freedom Fighter and love interest for Sonic and giving her a fairly notable role in nearly every arc (ranging from main character to prominent supporting character). Granted in both cases there are still a fair amount of supporters, though it's obvious the fanbase is very polarized by their heavy usage in the comics.
If you want to get technical with the usage of Knuckles and the expansion of the Echidna civilisation, consider the following: Ken Penders has stated, flat out, that he doesn't use characters that other people created and in turn, considers things that people do to his own characters non-canon. He has admitted that the first character that he used that wasn't his or already pre-established was Mina Mongoose in issue 150note which isn't actually true, as he'd apparently forgotten his use of Mammoth Mogul early in the Knuckles comic and proclaimed that, if he were to return to the comic, he would automatically make all of Ian Flynn's work non canon because they went against his pre-established ideas. If that doesn't scream "Creator's Pet", nothing will.
Here's one more issue people have: Penders has stated that Archie can use his characters again if certain conditions are met, one of them is making his Mobius: 25 Years Later story the canon future of the book. Aside from that story having Knuckles be the one the ultimately kills Eggman and the Sega characters getting married off with babies. Not only would this drive fans absolutely crazy with Shipping Wars, it's also meant to be a prequel to The Lara-Su Chronicles, a story that Penders is working to get published through a different company and stars Knuckles' daughter. Thing is, Penders can only publish TLSC if it doesn't resemble the Sega-Sonic art-style and isn't tied directly to the Sonic books. So the condition about 25YL is just him forcing his vision on the book for personal reasons.
Drift from IDW's Transformers comic hit this status before he even debuted because the promotion of the character was so obnoxious. He was hyped up at conventions as "The Wolverine of Transformers," which struck many fans as odd because Grimlock has a lock on that role. Drift has a Weeaboo vibe thanks to the rising sun motif and Gratuitous Japanese on his car mode, as well as being described as a "drift-racing Transformer" created because he filled a niche no other character could (never mind the Loads and Loads of Characters in Transformers and the fact that at least one drift racer already existed). He boasts Implausible Fencing Powers, an annoying arrogant smirk that never goes away, and copious shilling from fan-favorite Kup. He debuted alongside the Wreckers, a group of well-loved badasses, with no explanation except that everyone thinks he's so awesome. There are even instances of characters asking where he is when he's off screen. Oh, and did we mention that he's some sort of mysterious wild card who is not really an Autobot but is trusted by Kup and company anyway? Essentially, he's a heavily promoted character who is cool because the comic tells us he's cool and lets him curb stomp scary Insecticon drones (while wearing that Primus-damned smirk) and impress the actually likable characters. The similarity to The Simpsons parody of Creator's Pets has led Transformers fans to start a meme of quoting "The Itchy & Scratchy & Poochie Show" in reference to Drift, hoping desperately that his home planet needs him and that he dies on the way back.
Shoehorning Drift-chan in the children's "I Am Optimus Prime" Robot Heroes book sure doesn't help his case any either. And he does nothing, he's just there because we're supposed to believe he's awesome. The Transformers Wiki even gives as picture captions, "He's your horrible fancharacter." and "Seriously, you made this guy up when you were eight."
One of the biggest problems with Drift is that he's not only writer Shane McCarthy's awesome fancharacter, he's also become editor-in-chief Chris Ryall and editor Denton J. "Doubledealer" Tipton's pet character. Hence his inclusion in the children's book "I Am Optimus Prime" (ensuring kids reading the book would remember the awesome character that IDW invented) and under Tipton's penmanship, ended up having his horrible advice taken by Perceptor over the veteran, experienced Kup's more sensible advice, abandoning science in favor of becoming a dull "sniperer".
And yet, to everyone's great surprise, his role in The Transformers: More Than Meets the Eye has managed to overcome a lot of the hate he generated under less competent writers. He get's some holes punctured in his incessant moralizing, his spiritualism is written with a more humorous air, his backstory gets some nuance to it, and has some horrible consequences of his well intentioned actions coming back to bite him in the ass and leave him cast adrift. Even the Transformers Wiki admits he's a much more tolerable, if not outright enjoyable, character.
And then McCarthy got another shot at writing Drift, in a four-issue miniseries, for reasons known only to IDW's higher-ups.
Bumblebee became this throughout the Costa run. He'd been basically well-liked beforehand under Furman, as an understated and fairly cool character who pulled off an awesome fight scene against Skywarp in the first miniseries. When Costa got his hands on him, he kicked off a very long arc where Bumblebee became the leader of the Autobots. Fans were incredulous about it as anybody, especially since Bumblebee had never been very highly-ranked or very important to the plot, with many blaming Adaptation Displacement from the films. Pretty much every single story arc featuring Bumblebee was based on the exact same plotline over and over: people aren't sure if Bumblebee should be leader, Bumblebee mopes, Bumblebee does something supposedly cool, everyone agrees Bumblebee should be leader. On top of that, he also turned from a tenacious and somewhat pragmatic scout who was viewed as an equal by his fellows to a whiny little kid who felt more like a mix of the worst traits of every 'Bee except the one who'd been featuring in comics a few months ago. This plotline continued over dozens of issues, and it wasn't until late in John Barber's run that 'Bee finally started to dig his way out (most agree that he finally escaped with his Goldbug upgrade, which coincided with him being ousted). And then, in The Transformers: Dark Cybertron, he dies.
Xander Payne from Mega Man was loved far more by then-editor Paul Kaminski than most of the fans, who find him boring. Word of God states that writer Ian Flynn had to tone down most of Xander's appearances in Worlds Unite due to Kaminski giving Xander way more screen time than even the main characters of both the Sonic and Mega Man comics themselves, to the point where Xander was practically the main character of the crossover.