I actually think we can make a pretty good case for Toga being the best written female character in all of Boku no Hero Academia.

There are two other contenders–Inko and Nana–who could probably easily take the spot if not for their extenuating circumstances: Inko simply isn’t in the story enough to be a consistent source of emotional engagement, and we haven’t seen enough of Nana yet to get a real sense of the depth of her character. If Nana gets to be part of an extended series of flashbacks or becomes a vestige that Izuku can talk to, we might get enough of her to bump her to the top.

But right now, I can make a pretty convincing case for Toga.

1) She is the only female character whose actions are absolutely central to the main plot/conflict as it is unfolding right now. In the last 100 chapters, the only female to single-handedly accomplish anything for her side of the conflict has been Toga. You could not remove Toga from the plot and replace her with any of the male characters around her because her quirk and involvement in the story line are actively integrated in a way that none of the other female characters’ are (again, barring Nana). Mina? Jirou? Kendou? Uraraka? Tsuyu? Even Momo? In the last half of the manga’s plot, none of the class 1-A or 1-B girls have played any major part in the series’ overall conflict, had any stand-out moments of emotional depth that wasn’t narrated
for them by a male character, or even been allowed to meaningfully contribute to the battles except during training against classmates, the outcomes of which have no lasting impact on the main heroes vs. villains conflict.

That’s because Toga doesn’t suffer from the one thing holding back all the heroines and heroines-in-training: good girls aren’t violent. Good girls are lovable, attractive, and supportive. They’re not ambitious or obsessive about strength and overcoming their rivals like boys are. Good girls behave well. And unfortunately, Horikoshi is pretty progressive in some ways and really, really unprogressive in others. His definition of “good girls” and the ways good girls act seems to be pretty rooted in conservative Japanese standards, which traditionally have undervalued women. (This is not to say that everyone in Japan discriminates against women, far from it; in general, however, societal standards for women in Japan have lagged behind other major developed nations.)

Uraraka and the other girls in 1-A and 1-B can and will become heroes, surely. They can even prove themselves to be very strong and skilled individuals. But they will only rarely–if ever–be allowed to outshine their male compatriots in terms of strength, aggression, impact on the main plot, and even emotional depth. The tension and depth of this story has, so far, been given almost entirely to male characters–Deku, Iida, Bakugou, Todoroki, Shigaraki, Kirishima, even Shinsou… Readers get more glimpses into the mindsets, emotional struggles, and backstories of these characters than any of the girls. Bakugou can literally cry and scream on screen from how angry he is that he doesn’t measure up to his classmates; but Momo, who feels similarly, will demurely have her confidence issues discussed by Todoroki and Aizawa for her.

Toga, however, doesn’t get hit by this stuff quite as bad because she isn’t a “good girl.” Toga can be violent. Toga can be out on the frontlines throwing down directly with the male heroes and can come out on top because she’s a villain and sometimes the villains have to win for the story to be exciting.
Toga got away with threatening Shigaraki.

Whether Tomura is just telling lies to keep her on his side of not, Toga is canonically referred to as one of the League’s “linchpins.” She’s tangled with the heroes two more times than Dabi, Mr. Compress, Magne, or Spinner, and once more than Twice, making her literally the League’s most active member. Because of her role as a villain, Toga is free from the limitations that prevent the heroines from making any lasting impacts on the plot.

2) Toga’s personal motivations/mindset have direct impacts on the plot. Sure, being a “love obsessed” girl who develops crushes at the drop of the hat isn’t exactly the most fantastic basis for a female character ever–it’s cripplingly stereotypical and a gross excuse to draw faces bordering on ahegao, actually–but at least Toga’s crushes are plot relevant. Her “love” for Izuku and her collecting his blood lead to her utilizing that blood in combat to directly change the course of what is probably the series’ most important and dramatic battle to date. Unlike Uraraka, whose crush is essentially mandatory due to her role as the love interest and really has no bearing on the major plot, Toga’s “love” for Izuku shapes not only her actions but also the actions of others because she is a mover-and-shaker in the main conflict, until other female characters.

Toga’s crush on Stain was what drove her to join the League, despite the fact that Stain is no longer part of it in any way–and she’s remained loyal to the League. Her crush motivated her to take direct action and change the course of her life. Unlike other crush plot lines given to female characters, which are often used only in two contexts: 1) Oh no, I can’t let these feelings affect my friendship with [shounen protagonist]! 2) Ha ha, look how adorable I am trying to hide my crush from everyone!, Toga’s crushes are driving factors in the plot overall.

3) Toga has demonstrated more meaningful emotional depth than half the female students. You’re right–reducing Toga to fanservice badly degrades a character who’s actually been painted with more depth than virtually any other female character (except Inko) in the series so far. In her response to Magne’s death, her comments that she wants to continue enjoying life with the League, her willingness to threaten Shigaraki for making choices for her, and her delicate treatment of Twice, Toga’s feelings–even those beyond her love and friendship obsession–are portrayed seriously and with a degree of attention and agency that few other females in this series get. Toga is loyal, intelligent, dedicated to pursuing her personal goals, empathetic, brave, and strong-willed, and most importantly–these aren’t informed traits. We don’t hear about how smart she is or how nice or how brave she is from other people–we see it in direct action throughout the course of the story. You don’t hold a knife to Shigaraki Tomura’s neck without being both staggeringly courageous and dead-set in your beliefs–Toga has a backbone of steel and a good head on her shoulders. She’s in far more control of herself than anyone is giving her credit for; she knows exactly what she wants and she’s going for that without hesitating. Her response to Twice after Magne’s death
not only

demonstrates a clear understanding of other people’s feelings, but also signals to the readers how far the League has come in supporting and valuing each other, an important turning point for readers, making her feelings and dialogue more meaningful than many of the other female characters’.

4) Toga’s obsession with identity–and its ties to her quirk–implies a significantly more interesting backstory than most other girls in the series. In a way that doesn’t happen for many other characters outside the villains, Toga’s quirk is directly tied her to mindset and behavior. She is obsessed with seizing the identities of the people she “loves” to actively become those people. It should be obvious that this obsession is a direct off-shoot of her powers. Imagine what life would be like for a child who could literally change identities any time she became dissatisfied with herself. Forming a personal identity is a complex process for human beings (google Erik Erikson’s Eight Stages for a more in-depth look), and it is also a process fraught with peril. Children and young adults who fail to develop healthy, complete self-identities struggle in a variety of ways, not the least of which is mental illness. How would a tiny young girl who was capable of completely altering her physical appearance and attitude, enough so to be easily mistaken for others, define her own personal identity? This is literally a nightmare scenario, ripe for the development of psychological issues. It wouldn’t surprise me to find out the start of Toga’s descent into madness was realizing that, by hurting others, she could become someone better, more popular, with more friends–someone happy. It makes perfect sense that Toga is the way she is now, with the quirk she has. Toga’s desperate love–her desperate desire to be someone else–is almost inevitably going to be tied to a shattered sense of self. This is why the issue of “villain quirks” is so interesting–did Toga ever have a chance to be “normal,” with a quirk that would have devastated the psyche of a growing child?

I don’t know when or if we’ll ever see Toga’s backstory, but just the hints we’ve been given are already enough to make it richer and more interesting to think about that almost any of the other female characters in the series.

Toga is great, and seeing what she gets reduces to by the fans (hell, and her own creator sometimes) seriously bums me out.