The Furtopia Darwin's Soldiers RPs has Dragore, who fits this trope perfectly. He is a major Mary Sue and a scrappy with a big role, adored by the creator and steals the spotlight.
Lupis from the rebooted Furtopia RP is even worse. He literally hijacks the entire story and the plot shifts from a focus on the terrorists to the rogue scientists, who were originally in the background.
Diedrich of Gaia Online gets a lot of hate from users who find his personality quirks obnoxious, and are sick of seeing him shoehorned into one event after the other.
A rather large part of the Happy Tree Friends fanbase view Lumpy as this. While he has his fans, it doesn't help that there were only two TV episodes Lumpy didn't appear in. In some of these he didn't have much of a role other than just to be there. This is only justified by the fact that the writers seem to work on a "take the dumbest character in the series and throw him into jobs that require brains and see what happens" system.
Ronnie the Skeleton on The Irate Gamer. He is a Jewish stereotype who was hated from his first appearance, where he was given an extremely Overly Long Gag regarding talking non-stop on the telephone. It seems none of his fans or non-fans like him, yet Bores is attached to him so much that he'll put him in any possible place, like having this already hated character do things like host a Christmas Special and save his life.
One of the recurring complaints about Marvel Super Heroes: What The—?! concerns the fact the ugly and obnoxious M.O.D.O.K. appears in nearly every episode. Despite this, Marvel still gives him a frequent amount of scenes.
MLB Trade Rumors publishes a number of articles based on players' agents despite the fact that the comments for them are the lowest on the site. Simply put the viewers don't care who represents who (with the exception of super agent Scott Boras, or recently when Jay-Z became an agent).
Porn example: Sara Stone on Naughty America. After being gone a few years, she returned to the biz with a "exclusive" deal with the site. As expected, she had a couple new scenes... then more and more and more... to the extent that if there was a possible sub-site/genre she could be placed in (ex. threesomes, cowgirl as in the occupation, cheating wife, etc.) you could best believe she was there, sometimes two scenes of her per week. This isn't to say that she was actually bad in said scenes, but the viewers called the site on it and eventually the frequency died down along with the exclusive deal.
Certain Neopets rank low in popularity, but seem to be favorites among the creators. The chia (currently ranked 31/54) and blumaroo (36/54) both pop up far too frequently on the site in the form of NPCs, special items, location art, and the like. On the other hand, the chia was the first Neopet created.
The biggest example on the site is probably AAA, the game master. Not only is he an insufferable prick, but his challenges also directly cut into the various plots on the site, forcing them to be rushed. Considering that the plots and their associated puzzles were some of the highest draws on the site, many fans cried foul.
In a sense, "Archived" objects from the SCP Foundation are this. While most of them aren't considered terrible or as bad as the Decommissioned SCP items, they are generally considered weaker than the main list items (mostly due to suffering from Early Installment Weirdness) and one the reason they haven't been deleted is the site staff want to keep them around either for personal reasons or due to their involvement in various tales.
Zapdramatic desperately wants the viewer to sympathize with Ted Hartup from Ambition. Keep in mind the guy starts out trying to get his kids back from his ex-wife by going to her office strapped with dynamite to hold the entire floor hostage by threatening to "blow us all to hell" while ranting that he's a victim of some kind of conspiracy, and after he's arrested starts regularly escaping from jail (the first time including assaulting a police officer) and at one point threatens the player with a gun (and even accidentally kills them if they say the wrong thing.) Zapdramatic soon tries to paint him almost like some kind of Hannibal Lecter-style intellectual who's always right and regularly abuses ten-dollar words. Early on, the player has to interrogate him and rule that he's perfectly sane, which in the world of Ambition, means that he's excused of every criminal act he commits because he's an innocent victim being played by sinister outside forces, instead of being criminally responsible for his actions like it works in the real world. It gets even better when Duke Crabtree forces you to go along with a plan to frame either Ted or Yale for a murder. Trying to frame Ted locks the player into a no-win scenario while the game chastises them for trying to frame poor, innocent Ted.
Bonus points for there being strong evidence that Ted is Zapdramatic's Author Avatar.
Sir Basil Pike Elementary has Janina, who seems to be a stand-in for Zapdramatic's daughter, in a series that was apparently made to help her cope with bullying. Only the series does nothing to make Janina at all likeable, with her constantly spying and butting into other people's problems and snarking at them. She's supposed to be a big up-and-coming musician, but her only song can't decide whether it wants to ripoff "Enter Sandman" by Metallica or "Animal I Have Become" by Three Days Grace, isn't very good, and comes with a very confusing music video.
Death Battle has been met with accusations of favoritism towards Rooster Teeth characters due to the fact that both ScrewAttack and Rooster Teeth are owned by Fullscreen. The accusations were first leveled during the Yang Xiao Long vs Tifa Lockheart battle which saw Yang defeating the busty brawling barhop, which fans of FFVII accused ScrewAttack of being nothing more than shillers towards RWBY to promote Volume 3 of the series, which was released a few days after the video was released. The biggest complaint is that Yang shouldn't have fought at all (or at the very least, not fought Tifa) because she only had two volumes under her belt; this is discounting the fact that Rainbow Dash was used in a Death Battle with only one season completed and its second season barely started. This was increased with the special Death Battle crossover with Red vs. Blue, which pit The Meta against Agent Carolina.
To a lesser extent, a number of fans will accuse the creators of favoritism towards the winner of any given match up when their favorite character loses.