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. 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 Jerkass, and both Mina and Allan leave Orlando. It's implied their attractions to Orlando were infatuations with Orlando's novelty, and that the novelty wore off surprisingly quickly offscreen.
The creators perhaps realised and acknowledged this to a degree; one of Orlando's characteristics is switching genders from male to female and back every so often. It is noted in the text that Mina likes Orlando more when female than male, and perhaps accordingly, male Orlando tends to be a smug, preening dick but female Orlando is generally more humble and likeable.
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 (Archie Comics) 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.
Of the various echidna characters, the most infamous Creator's Pet is probably Locke, Knuckles's Disappeared Dad. Penders loved the hell out of Locke, having him inflict The Worf Effect constantly on other characters and get the focus in a lot of storylines while other people chatted him up. Most fans really didn't share that opinion, given his self-superior attitude, his borderline sexist behavior, and his actions making him Unintentionally Unsympathetic—his major character moment is that he had a bad dream that he thought was a vision, which caused him to mutate his unborn child with radiation to turn him into a superbeing, and then he faked his own death in front of his son and vanished for decades to better manipulate his son's development. Penders apparently based Locke on his own issues with his dad, and claimed it was meant to reflect those issues... but it falls rather flat when Knuckles bears literally no ill will towards his dad and thinks he's the greatest guy ever.
Novas Aventuras de Megaman was not exactly what you would call "critically acclaimed" to begin with, but things only got worse with the introduction of the character Princess. She's violently psychopathic, unpleasant, and an obvious mouthpiece for the author's views, starting with a completely plot-irrelevant rant about the need for more comics featuring Brazilian characters, a rant which includes the tasteful use of the word "retarded". Infamously, the author flat-out admitted, in the grand tradition of all bad fanfic writers, that he was going to have her kill off all the other characters (yes, including all the Mega Man cast) and make it a series all about her instead. Fortunately, the horrified executives quickly kicked him to the curb and fastball-pitched Princess right out of the comic.
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 numerous 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 gets 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 come 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.
Spike Witwicky got a Retool in All Hail Megatron from the inoffensively bland Tagalong Kid in the original cartoon to being a generically "badass" American soldier. Aside from debuting in a disliked series, his flippant and crude attitude — meant to come off as a devil-may-care roguishness — instead read as irresponsible, entitled, perverted, and shiftless, not helped by him being a general's son. He then received a prominent role in Costa's ongoing, being appointed to an important job that he was clearly not competent enough for, and much like Bumblebee, swiftly became its most loathed character. This culminated in an issue where he went off on his own to hunt down, torture, and execute a Decepticon while delivering a hideously poorly-written"The Reason You Suck" Speech about how Muggles Do It Better. The fact that Costa was delivering interviews at the time about how he didn't really like writing Transformers and couldn't see why people sympathized with them, and an editorial edict that Spike's haircut had to stay consistent in an era where characters' entire designs◊ had a habit of completely changing issue-to-issue, pretty much sealed the deal for him. Thankfully, towards the end of the run and with the beginning of the Barber-Roberts era, they realized this and started writing him as a straight-up villainous Smug SnakeHate Sink — and it's quite telling that they had to change almost nothing about him to accomplish this, other than having the other characters finally react to him being a violent, self-centered asshole.
Xander Payne from Mega Man (Archie Comics) 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.