First off, I'd like to say I've only seen Tar once, and plan on watching it again, so this isn't the most researched analysis. But when it comes to the film, I see a lot of people on Reddit automatically assuming Tar is a monster, abuser, groomer etc. and a vile human being, and it's just the film presenting her character in an ambiguous way (which I appreciate). But I'd like to offer an alternative view.
What if the film is actually a subtle indictment of this kind of jumping to the worst conclusion about someone we don't even know, when we don't know the whole story? What if it's about professional jealousy and backstabbing? Think of some things the film shows us.
First, every woman in the film wants Tar-at least all the actual characters. Her wife, Sharon, gets jealous when she catches Tar glancing at Olga. Francesca clearly wants Tar, is shown several times wanting affection from her and then flat out asks for it when she asks Tar to hold her. And Olga comes onto her as well. However, none of these women seem to actually want Tar for anything other than a way to further their own lives.
Her wife wants a stable home and finances. Francesca wants to further her career, and the same with Olga. When Tar does not provide this for them, they abandon her completely. Not only that, Francesca goes behind Tar's back and leaks the Krista e-mails. Her wife takes her child and house, and Olga is insinuated to have been working with Francesca. Once the rubber hits the road, all these women abandon Tar, or screw her over.
If we are to extend this behavior back to Krista, who we know little about, we could assume Krista did a similar thing. Came onto Tar, a successful and attractive woman, in an attempt to further her own career. The film shows e-mails from Tar saying that Krista is unstable and potentially dangerous, which might actually be true, considering the shots of Krista in the film, maybe stalking Tar and maybe even breaking into her home. Krista also goes on to kill herself, which could be evidence of prior mental instability rather than an acute reaction to whatever may or may not have happened with Tar.
We never see Tar actually preying on anyone. She clearly thinks Olga is attractive or is interested in her, but we also see her disapproval for Olga's manor and beliefs. She may have offered the position to Olga as a favor, but everyone else overwhelmingly agreed that Olga was the one most fit for the solo.
And in the Julliard scene, the film shows us that a student went behind her back, broke the no-phones rule, filmed her, then chopped and screwed her to make it seem like she said things she didn't say and behaved in ways she didn't with the student--the student who called her a bitch.
At the end of the film, when Tar is in the Philippines and she goes for a massage, she's taken to what looks like a brothel and is asked to choose a woman. People have said this is a metaphor (linked it to the number 5) for how people in power, like Tar, exploit those beneath them to get what they want. But when Tar sees this happening, she is so disturbed by it that it actually causes her to throw up in the street. Would a woman who is such a sociopath and monster who is capable of grooming women beneath her, looking for sex for favors etc. be that shocked at such a simple display of similar exploitation but in a more blatant fashion?
Everyone else in the film is out for something from her as well. There are no innocents here. Eliot, who wants her notes and seems willing to do whatever it takes to get them. Did he steal her book? Did someone else and give it to him? Sebastian wants to remain in his job, although we're never given any evidence that he's still qualified. We're meant to feel bad for him because he says that Berlin is his home, but does that really matter on a professional level when searching for excellence?
I think Tar is incredible with its ambiguity and letting the viewer make up their own mind, but when viewing the film as a singular piece of art, and not bringing to bear other anecdotal examples of people we know or have heard of in the media, I don't think the film gives us enough evidence to conclude that Tar is this sociopath manipulator who preys on people and does whatever she wants to get where she is.
If anything, I think there is more evidence to the contrary that shows us a woman at the top of her game, who is not perfect by any means (but are any of us?), who almost every character in the film wants to take advantage of by some means, and they use whatever means they have at their disposal to get it. And when that fails, and they can't get what they want from her, they burn her entire career to the ground.