Board Thread:Manga/@comment-27321453-20191208140701/@comment-24407809-20191210235736

Even by that definition, Gabi is not a Mary Sue (the below text is copied and pasted from a previous forum thread, because this conversation keeps coming up for some reason).

The definition of a Mary Sue is "an idealized and seemingly perfect fictional character" who can "usually perform better at tasks than should be possible given the amount of training or experience, and usually are able through some means to upstage the main protagonist of an established fictional setting, such as by saving the hero."

With this in mind, I would say that Gabi is actually a subversion of the Mary Sue trope. Whereas Mary Sues are characters who are impossibly good at tasks that they have no training for, Gabi is a character who was introduced as being at the top of her class in the Warrior Cadets who has utterly failed at everything she has tried to do since the battle of Liberio. The last thing she was successful at was blowing up the armored transport in For Slava, and since then it has been one failure after another. She boarded the zeppelin to kill Eren but only succeeded in killing one soldier, and then had to be saved from being shot by Falco. She managed to escape her jail cell, but then got utterly lost and had to be rescued and taken care of by the Blouse family. She was completely inept at doing farm work while living with the Blouses, and when she tried to get help from Niccolo she had to be saved from him by Falco. Then she had to be saved again from Kaya by Mikasa and Mr. Blouse. Then she had to be saved from Eren by Pieck.

Gabi is so incredibly inept that it's almost comical. Her entire character arc during this final arc revolves around being completely humbled by the fact that she can't do anything right, and keeps getting the ideology that she grew up with (all Eldians are evil) proved wrong the all of the good Eldians living on Paradis.