Aya from Touhou could be debated as the whole opinion is based on fandumb.
Appearing in various games? She's a reporter who likes incidents. Unfortunately for fans of other characters, those characters are servants basically mainly doing their own thing until an incident affects their sphere (spirits in Ten Desires is why Youmu's in the fold).
Mountain of Faith's incident mainly affected Reimu and the Tengu (Marisa's appearance was her going along/getting dragged into things)
These days people have warmed up to Aya pretty well with the main contention point more her fanon rendition (Paparazzi nut) than anything.
Aya's own game? It was something ZUN slapped together to go with the book, using (most likely) cutting room floor spell card patterns (without Aya's bullet Erasing Camera, they'd be impossible to dodge!)
Holding back? That's the point of the spell card system, an easy going way to balance things. That's also overlooking Reimu's infamous laziness and how her raw talent is what allows her to win so much. That and as a 1000+ year old Tengu, one'd figure she'd be pretty strong (Suika who's about as old is widely believed to be one of the very few that defeated Reimu), justify her difficulty even if she was merely putting on a show.
Though I must say Sanae's flirting with this status now, particularly with all the focus she's getting and how she's able to keep up with Reimu and Marisa despite being quite a novice (Before Mo F, she was basically a school girl/real life shrine maiden). This in turn has caused fan game/material makers to favor her heavily/unfairly in turn. Another Broken Base right here.
There's also a some fans who aren't amused with where the character development has taken her: She's getting steadily quirkier (possibly forced) in personality and more zealous in "youkai extermination". It's to the point where Hatate in Double Spoiler remarks that one of Sanae's spell cards' effects (sucking up youkai's energy into herself) makes her "not human, not god, but something more evil". While she's rather popular in the west (for reasons both clean and fetishy), she seems to be falling in the japanese polls.
Update: seems with the recent games, it's getting turned around to a partially perplexing extent.
Edited by 216.99.32.43
It's super effective.
Examples Are Not Recent. Which expansion pack is being referred to in the Warcraft example?
Regarding Abby, one of the requirements for Creators Pet is that they are "put in big scenes for no reason", but Abby is one of the principal characters, meaning that she has a reason to be in big scenes, so shouldn't she not count for this?
I can't draw