@Ebalosus
The “Outsider” aspect of sues isn’t acknowledged nearly enough, it really should be a core, well-known part of the concept as opposed to an afterthought allowing this kind of “Mary Sue means character you don’t like” thinking to happen.
By definition, the term was invented because of Star Trek
fanfiction, because of a character being inserted into an already established universe by a novice and/or biased creator showing poor understanding of basic writing techniques and character development.
However, this can also apply to “professionals” that have their work made “official” by the holder of the IP’s rights, so basically anyone that wasn’t part of the original team.
That’s why characters like Batman, Superman and Twilight Sparkle cannot be sues, because they’re part of the
core experience, if they’re not liked, then… why be a fan in the first place? To be a sue, a character needs to be
added into an IP, either officially or not.
Elizabeth is kind of a complicated case, since Bioshock Infinite hardly took anything from the initial games, it might’ve as well have been a new IP, in which case, she’s part of the core experience, her being a space and dimension travelling anomaly hasn’t been added on top of any well-established lore.
And then Burial at Sea shat all over that concept and linked both universes, in which case yes, it is now possible to consider her to be a Mary Sue since she’s been retroactively added on top of the standard Pre-Infinite Bioshock lore, and now has the entire series orbit around her actions.