Oh wow, it's much worse than what I've got from reading the plot in Wikia. That's Steven-Universe-tier bad.
The popular manga Attack on Titan has recently ended with a chapter 139 and has received a mixed reaction from fans, with some of the fans being really disappointed and voicing their frustrations all over the internet. The main criticism is that this last chapter assassinates the characterisation of some of the characters of the manga, including the main character, Eren. A part of the fandom speculates that this is the result of the ending being rewritten from a darker, more depressing ending, to a more happy-ish ending. I don't want to talk about the quality of the ending in general, but rather how the last chapter has betrayed its female characters and the manga's earlier anti-war and anti-genocide rhetoric. Warning: manga ending spoilers ahead in the rest of this post! CW: abuse, genocide
1. Female characters
There are three female characters that I think the last chapter betrayed in particular. First, Ymir; Ymir is a thousand year old girl with god-like abilities; however, she is also a slave to these abilities. The main character, Eren frees her from this slavery and asks her to help him commit global genocide (more on this later). Initially it seems that she helps in committing global genocide for two reasons: because she values freedom greatly and global genocide is a way to free the oppressed group Ymir and Eren belong to; and also because she wants revenge on the world. Before becoming a god, Ymir was a slave, owned by a man named Fritz who abused her, raped her and who kept her as a slave until she died. In the last chapter it is revealed, however, that Ymir did everything she did because she was in love with Fritz. I consider this a betrayal of her character, because it makes her, incapable of acting on her own, clinging to her abuser for thousands of years. Also, her strong yearning for freedom is removed: while previously it was shown that she is willing to risk her life to free some pigs from being slaughtered, now she doesn't care about freedom at all.
Second, Historia: Historia is the queen of the nation of Eldia, and the descendant of the Royal Familiy who possess magical powers. In the last arc she was hinted to be pregnant with Eren's child, however it turns out in the final chapter that she was pregnant with somebody else's child and her pregnancy ultimately is a red herring and doesn't add anything to the plot. Why is this a problem? First of all, a main character got completely sidelined to be pregnant for the duration of the last arc and does nothing, even though she is the Queen and the descendant of the Royal Family. Just as with Ymir, this removes her agency (but this would have been true even if she was pregnant with Eren's child). Secondly, the problem with Eren not being the father is that instead the father of her child is a former childhood bully of her. Just as with Ymir, an abuser is turned into a lover. While not as big of an issue as with Ymir, we are starting to see a theme her with female characters and unfortunately the same holds for the final female character, Mikasa.
Mikasa is Eren's foster sister, who is also in love with Eren. Her love is extremely obvious and Eren is shown not to reciprocate romantic feelings for here throughout the series. In fact, Eren tries to get stronger and become more independent from Mikasa. However, in the last part of the manga their paths diverge and Mikasa can't follow Eren's descent into global genocide. In fact, in the penultimate chapter Mikasa kills Eren. So what happends in the final chapter? Here it is revealed that Eren was madly in love with Mikasa (with no prior build-up) and that Mikasa cannot move on from Eren. Why is this a problem? Eren pushed away Mikasa before, going as far as calling her a slave and saying he always hated her. Again, Mikasa feels romantic love for someone that emotionally abused her. Unlike the other female characters, Mikasa has more agency, as shown in her killing of Eren. Ultimately, however, Mikasa cannot move on from Eren. I think this is a kind of lack of agency: Mikasa cannot be her own person, she is still tied to Eren.
In conclusion, the last chapter makes the female characters be in love with former abusers and by doing so, removes a part of their agency.
2. Anti-genocide/anti-war themes
The main character, Eren, commits a race-based global genocide and kills 80% of the global population. He does this because the world wants to kill his race, the Eldians, and he feels that destroying the hateful world is the onlly way to save himself and his loved ones. He is shown as a villain throughout the final part of the manga (except for the last chapter). He is shown to be in a state of depression over his actions, he doesn't want to do what he does, but he feels compelled because Eren wants certainty. He wants to make sure that his friends live and the only way to be certain is to kill everyone, even those that are innocent. But doing so destroys him inside. Even so, he keeps doing what he thinks is necessary. The manga shows this in a negative light: this global genoicde and Eren's actions are presented as the consequences of a world filled with racism, hate and war. In other words, if we can't stop racism, hate and war, we will have to fight until ultimately only one group survives. And this is bad for everyone, even the victors: Eren is mentally unstable and depressed and his supporters are shown as fascists. However, the last chapter reveals that Eren planned to lose and did it so that his friends could kill him and be heroes. His friends thank him for committing global genocide (!) so that they could live. Eren was a villain who became who he was because the world of Attack on Titan is an awful place─ retconning him to be a hero is non-sensical and paints his genocide in a positive light, when it was cowardly and an act of ultimate desperation.
In the end, I do think this ending wasn't the original ending. To me, this apparent last-minute change has completely messed up one of the main themes of the manga, which was decidedly anti-war, anti-genocide and anti-racism.
There is much more that could be said about this manga and the ending. I just wanted to add why I was disappointed with it from a social justice perspective; I think that this kind of critique wouldn't go well in the attack on titan subreddits and I just wanted to vent somewhere. The only hope for this great piece of work is that the anime adaptation fixes the ending.