In the Living Death campaign the character of Jason Lindaman was supposed to be a super-intelligent, Crazy-Prepared investigator who was taken out by the enemy before the PCs arrived. Because the PCs' only real interaction with him was after something heinous that took all four to six of them to handle had physically or emotionally crippled him, many players considered him a joke and/or incompetent to the point that they wished for his death.
Elminster from Forgotten Realms. For the crowd that is not into roleplaying: Think about what would happen if Gandalf was the main character of Lord of the Rings and the story consisted of him beating up anything that is a bother and boning the goddess of magic whose boobs are totally big and rad to the max.
Part of the problem is that Mystra in turn comes across as very much Ed Greenwood's pet goddess, so much more powerful than any of the other gods (the introduction to Shadows of Doom comes right out and says so) that she basically has to deposit parts of her own godly power in her mortal Chosen. Like Elminster becomes at the end of The Making of a Mage. So Elminster's problem is, in part, that while other famous Forgotten Realms characters may be people your player characters can look up to, try to emulate, and maybe one day catch up with... unless you can talk your Dungeon Master into allowing your character to enjoy a similarly "friendly" relationship with Mystra, El is always going to be Better Than You because the Realms' own canon Says So. (And as of fourth edition, that option doesn't even really exist anymore because, well, post-Spellplague Mystra is dead. Which has hit Elminster pretty hard as well, of course, but the damage is already done.)
The Necrons of have proven problematic for some fans. When the army got its proper launch during 3rd Edition, with a codex positing that the Necrons' undying C'tan masters were essentially the prime source of all evil in the universe, secretly worshiped by a pivotal faction of the Imperium, and responsible for the rise of Chaos, many fans complained that these Terminator knock-offs had usurped Chaos as the setting's Big Bad. The 5th Edition codex has attempted to rectify this by drastically reducing the C'tan's presence in the background, specifically with a retcon describing how they were betrayed and imprisonedby the Necrons. The book also assures readers that many Necron Lords have gone insane over the eons and enjoy delusions of godhood, and points out that what little the Imperium knows about the Necrons are mostly half-truths, lies, or flat-out wrong. Naturally, some fans are now complaining about the changes.
40ks oldest Creators' Pets have always been the Space Marines themselves. As Warhammer 40,000's mascot characters, the Space Marines get the most exposure and the most updates, while Codex Creep ensures that they remain a potent force on the tabletop. In the setting's narrative, Space Marines are so awesome that they've been awarded the "moral victory" even when they failed a campaign's objectivesnote this was probably because the Space Marines and Imperial Guard were lumped together (being on the same side and all), and the IG definitely succeeded in their primary objective. For their part, the Space Marines at least achieved their secondary objectives. Roughly half of 40k's armies are some variant of guys in Power Armor, and Space Marine merchandise sells more than all the other factions combined.
And then there are the Ultramarines, the Space Marines to the Space Marines. Thanks to letting an enormous Ultramarines fanboy do the writing, the Ultramarines have dominated the current Space Marine codex. Twenty-nine other Space Marine chapters are mentioned in the rulebook's background, and get a picture of their uniform and a paragraph or two of description - the rest of the book is all about the wonderful Ultramarines. The "Histories" and "Battles" sections of the book are devoted to the Ultramarines' exploits, while any other chapters get lumped into a comparatively brief seven-page section. Of the twenty-one pages of miniatures galleries, only two of them do not feature any Ultramarines. Of the special characters listed, half are from the Ultramarines, and half of those had not appeared in any previous edition. The Codex insists that even other First Founding legions, with their own traditions and proud histories, all aspire to emulate the example set by the Ultramarines. It even divides Space Marines into three categories: the Ultramarines and their successors, Space Marines from other gene-stock that try to be Ultramarines but can't due to their defective blood, and "aberrant" chapters who will eventually diminish in importance. Interestingly, before this the Ultramarines were considered kinda bland by many players, a generic by-the-book sort of chapter; now they have a massive hatedom and even long-term Ultramarines fans are annoyed by how much their army's being overhyped.
On the other hand, overrepresentation of Ultramarines in the codex makes sense because, being bland and generic, they are the most suitable baseline to compare the more interesting Space Marine chapters with; they are "normal" and "average". And their blue livery looks good as a default paint job for miniatures.
This was apparently a result of a last minute change, originally the book was going to be call "Codex: Ultramarines" much like the 2nd edition.
The newest Grey Knights codex - which was incidentally written by the same author as the latest Space Marine codex - introduced Lord Kaldor Draigo, who managed to one-up the Ultramarines through the sheer, over-the-top Sueishness of his accomplishments, which includes but it not limited to: surviving an endless walk through Hell, banishing a Daemon Prince in his first combat action, defeating a Daemon Primarch and vandalizing its still-beating heart, killing a Bloodthirster all but bare-handedly before stealing its unholy axe and reforging it into a sword with the power of his mind, and rampaging through the Chaos Gods' private demesnes without consequence.
In Warhammer Fantasy the Blackorc Warboss Grimgor Ironhide is hated by a large part of the fandom for replacing a black orc considered to be better thought through; the writers likes him enough to let him defeat Archaon, another badass character, and thus save the world by being badass.
The Elemental Heroes (and their spiritual successors, the Neospacians) from Yu-Gi-Oh! GX are certainly qualified here; already having a strike against them as the signature cards of the anime's unabashed Boring Invincible Hero Judai, they are absolutely reviled by most duelists due to their weak stats, underwhelming effects, their Fusions being unable to be summoned by fan favorites Cyber-Stein or Metamorphosis, and half of the Elemental Heroes being normal monsters. What pushes them over the edge, though is how throughout the show's run, Konami could hardly go through a set without dedicating at least a fourth of it to the E-Heroes/Neospacians and support cards.
Elemental Hero Mudballman is the king of this trope, being the only fusion with no actual effect, but still can't be summoned outside of fusion summon. At least Master of Dragon Soldier and Five God Dragon has reasonable effects to make up for it.
Similarly, Elemental Hero Flame Wingman and especially Elemental Hero Neos, as Judai couldn't seem to go one duel without using them almost exclusively. At least Flame Wingman remained silent, though; Neos also had the distinction of being The Obi-Wan since his introduction, and in seasons 2 and 4, he became a virtual Deus ex Machina, becoming "real" to take care of non duel-related threats. As you might have guessed, fans are sick of their overuse.
Synchros and Tuners are (albeit less commonly) hated by fans for similar reasons - they utterly dominate the plot and duels of 5Ds, Konami dedicates an average of three-quarters of a set to them, but unlike the E-Heroes, the majority of Synchros * cough* Dark Strike Fighter * cough* are on par with effin' Chaos, which either totally redeems them or makes them glaringly worse, depending on which side of the Broken Base you are on. in addition, XYZ monsters also seem to have taken this place as well, dominating the plot of the newest series Zexal, as well as getting put into every pack with effects that often make them more valuable than synchros, since you no longer need to use tuners or any other special cards or types in the limited deck space available.
Don't forget the predecessor of Synchros, Fusions. It's like the purpose of GX was to try and make them relevant. Never mind that you have to go through so many hoops to play them that Synchros were made to make them usable, every duelist in GX used them. Jaden's E-Heroes, as stated, most prominent.
AD&D 2nd Edition's Complete Book of Elves. This book caused some fan backlash over the text praising elves extensively, giving them superior knowledge of pretty much everything, moral sanction for everything (even for the arguably fascist grey elves, who kept slaves of other "lesser" elven races who were always inexplicably happy in slavery), the text outright insulting other races, and ignoring elven hypocrisy - this last one most evident in the sea elves, who went on great hunts that could depopulate a region of sharks but were given a pass on disrupting the ecosystem pretty much Because They Were Elves, so it was okay. Somehow. For some reason. Even the author eventually apologized for the Blade Dancer, a fighter/mage kit that gave lots of mechanical bonuses, with drawbacks that amounted to "things a Player Character was going to do anyway" (such as a tendency to being a badass loner who has spent years of Training from Hell before the campaign began, a tendency to rush off into an adventure if it seems that another elf is threatened, and focusing their skill in a single type of weapon), with apparent permission to derail the story by getting to determine for themselves whether a situation was even covered by their code of conduct.
"Kid geniuses" aren't as common as many people think. (Though they are often as annoying as people think.) Minors make up 14% of the Inspired population, with one genius in 50 being under the age of 13. These characters show a slight proclivity for computer science, with dimensional research also being popular.
The Old World of Darkness setting had Samuel Haight, arguably the worst Villain Sue ever published in all of pen & paper roleplaying. The writers just kept giving him more and more rule-breaking, crossover powersnote Sam was a ghoul, a skin dancer, a true mage who didn't suffer paradox, and the owner of a sword that let him steal even more powers and kept instructing GMs to ensure he lives for another adventure before they finally clued into the massive Hatedom he had accumulated and killed him off brutally. (Then, in the afterlife, he was turned into a (still sentient) ashtray.)
Some oWoD writers had a bad habit of doing this with any named NPC. Writer Dean Shomshak elaborates:
That's the other thing: WW hires people who want to tell stories. But, the only characters they have to tell stories about are the NPCs. So, they tell stories about the NPCs. Gods, I wanted to smack some of my fellow writers upside the head on some Vampire projects when they burbled on about the cool things they'd have Hardestadt do, or whoever. What were the *PCs* supposed to do?
This quote kind of sums up why this trope happens in tabletop RPGs in a nutshell — it's easy at times for writers of "official" game fiction to forget that even the most interesting NPCs they're writing about are technically only the supporting cast meant to help player characters said writers will never even hear about shine.
Both old and new World of Darkness can get into rather crippling "arms races" between creators and their pets. Every line has them, and the line developers will often slip into treating entire character types as their pets.
In Magic: The Gathering, there is a bet every new set: "Which new strategy will be so imbalanced that players will complain about how unfair it is and blame Mark Rosewater?" In the case of infect, Rosewater took blame because he loved poison counters so much.
A single character who demonstrates shades of this is JaceBeleren. In each story expansion, he's given more weight and his importance is emphasised. He's gone from being just one of the several new planeswalkers in the Lorwyn/Shadowmoor block to being so important as to be prominently featured in Return To Ravnica's promotional artwork.
Many fans feel Blue in general sometimes gets preferential treatment from the game designers; when Snapcaster Mage was printed, he was all the daily articles would talk about for several days in a row, and later articles would regularly bring up how great he was. Later, Snapcaster Mage's impact on the game was so profound that every expansion since has required several graveyard-hosers to counteract his power while he remains a creature that is seen in every format of play. Also, the card's ability was originally printed on a Red card, Recoup, gaining some resentment from Red fans.
Spellcasters in Dungeons & Dragons 3rd Edition and 3.5 (essentially, 3rd Edition Revised). One of the core rules' main designers was not subtle in his love for wizards, and hearsay claims he thought fighters needed to be nerfed (despite being one of the least optimal classes to take). More generally, spellcasting in 3.x is a versatile pool of abilities for almost any niche, and new spells in every book expanded caster options faster than anyone else. Wizards, clerics, and druids especially benefited - wizards just had to find or research a spell and spend a pittance to add it to their spellbooks, while clerics and druids automatically have access to all spells on their classes' spell lists. In the latter case this lead to the infamous "CoDzilla" (Cleric or Druid + Godzilla) whose abilities and versatile spell selection made them very easy to twink out - though wizards still tended to get more spells written for them in absolute terms.
A long-standing complaint of Legend of the Five Rings fans, though the Creator's Pet in question changes depending on the creator. Notable pets included:
Toturi. His faction got the story prize for the first arc despite another faction winning the tournament.
The Crane Clan, who got to avoid The Corruption running rampant during the second arc, to the point that a Bloodspeaker from a Crane family was printed as unaligned when every other faction got one.
The Phoenix Clan, who after becoming thoroughly corrupted and nearly destroyed, were given such a massive power boost that they completely dominated the tournament circuit for over a year. A number of powerhouse cards even received additional effects just before going to printing. The fact that the lead developer at the time was a longtime Phoenix fan had nothing to do with this, of course.