Note the specificity in the title: I'm not just talking about fictional characters with mental health issues (which is like 75% of all fiction anyway ^^; ) I'm talking about fictional characters who actually seek help with their issues, or give that help to others, as a significant part of the plot.
What are the pros and cons of depicting this subject matter? Which stories do you think do this particularly well, or poorly? How do you tackle it in your own stories?? I will be listening and taking notes 
I'm bringing this up because I recently started rewriting a story where the first half inadvertently turned into a "superhero/villain mental hospital" concept, which is SO surprisingly unique and intriguing that I'm seriously considering reworking the rest of the story to lean into it further. It's ridiculously fun; I don't think I've ever read or heard of a story that did anything like this.
Like, actually focusing on the therapy aspect and the emotional journeys of the characters; how they feel about their self-images and loss of autonomy; what they choose to show or hide during therapy in order to protect themselves...how much of their "therapy" is actually propaganda concerning their 'proper place' in society; whether or not they realize this, how this might possibly relate to therapy IRL...
...y'know, as opposed to just doing edgy 'insane asylum' schtick. And I am doing a little of that; I'm not better than anybody (¬‿¬) But there's so much more that I want to explore...
Anyway, to answer the other part of the prompt, I got some shows that have definitely already influenced me in this endeavor:
For instance, there's Undone (rotoscoped animated series starring Rosa Salazar; it's really cool and you should watch it), which approaches the topic of schizophrenia from pretty much every possible angle. ^^; And although Season 2 focuses more on the fantasy story-driven aspects of the plot, it also includes a stark look at what mental healthcare was like during much of the 20th century. Yeah, it's just a third of a single episode, but it's done really well, and its placement in the story gives it a feeling of tension that's just ~chef's kiss~ perfect. I have a feeling Season 3 will be a textbook example of what I'm looking for in this thread; I really hope they're working on it...
There's also Nikita (non-animated series in a totally different genre starring Maggie Q; it's also really cool and you should watch it) which is probably influencing my writing much more heavily. The way the antagonists approach desperate young people and mold them into loyal agents through training and "therapy", teaching them to find strength and self-actualization in their ability to complete difficult missions; exploiting their weaknesses, fears and traumas in order to control them, while presenting themselves as saviors, guardians, teachers, parental figures...it's great. ^^ A little campy, but solid character writing.
Because, as you might have guessed, I'm going for a 'toxic therapy' angle in my own story, the second example is much more relevant to the writing of my own antagonists. But the first example, showing how people can struggle with severe mental illness while still being relatable main characters, has helped a lot in the writing of my own MC's; I don't think the story would be the same without that influence.
Besides, I don't want to make the issue black and white...although it will be difficult, I'm striving towards an angle where the characters realize they were being manipulated and psychologically tortured, but still take some of the lessons they learned in "therapy" with them, recontextualizing them in a non-toxic way. Like, learning to open up to others, be vulnerable, analyze your thoughts and behavior...those are legitimately good things to do when you don't have an abusive authority figure trying to use them to brainwash you. ^^;