She’s certainly the character that I think they got the most wrong. Besides the general mannerisms, the fact that she’s all for torture and misc other shitty behavior feels completely off to me.
What do you mean by "most wrong?" Compared to her character in the book, or the character you'd like her to be instead?
I think Avasarala is actually one of the better written characters. As far as character development goes, she has one of the best arcs in the whole series. In the beginning, she is a politician and power broker who takes zero shit from anybody, especially the men who are supposed to be her superiors. Various tragedies like the Earth nearly getting wiped out nearly turn her into a bloodthirsty Belter-killing monster. She eventually softens substantially and only wants to do what's best for the human race as a whole. (But still taking shit from no one.) That she is an older Indian woman whose language would make a lumberjack blush is just an interesting twist.
One of the central themes of the Expanse (the books and the show) is that unlike most plots in books or movies, there are no good guys here. There are only people who are driven by some greater purpose (greed, power, loyalty to government, justice, etc). They do good things, they do bad things, they do stupid things. They are complicated, just like real people.
As an example, the characters that we might try to think of as the "good guys" are the crew of the Roci. Holden is a navel-gazing military wash-out who nearly starts an interplanetary war between Earth and Mars via pure speculation. And NEVER apologizes for it. Amos' background isn't explored in much detail in the show, but in the books he worked for a brutal crime boss on Earth and more or less just kills whoever gets in his way or because he thought they might. Alex was an absentee father and husband. Naomi abandoned her young child. And ALL of them stole their ship from the people of Mars. (They use the euphemism "Legitimate Salvage" in sorry-but-not-sorry kind of way.)
Finally, context is important. In the future of The Expanse, human civilization is pretty much A Fucking Mess. The Earth is overcrowded, half the population is on welfare, and crime is rampant. Mars is effectively a military state. In the Belt, you are as likely to die from a random equipment malfunction as saying the wrong thing in a bar. So a lot of parallels with countries in present-day Earth, just amplified.
Anywho, I don't agree with torture either, but it's hardly a surprise that it happens in that universe.
I love how you point out that the characters are all believable, flawed people. I love Avasarala's character (and the actress' voice on top of that is like icing on a cake), and the way she plays the Power game so well. I really dislike that her character would torture, but at the same time she's like a well-written villain. She doesn't quite fit on an alignment chart.
> ALL of them stole their ship from the people of Mars
I'm not sure how it is in the book, but in the TV show, a ranking officer of the Martian navy explicitly tells the ship that they are in control. As legitimate salvage goes, it seems pretty defensible. The only reason they don't go deeper into it seems, to me, to be because explaining that (and proving it) would be Very Hard, and they'd rather avoid the risk.
> a ranking officer of the Martian navy explicitly tells the ship that they are in control.
Yes, that's how they got possession of it and managed to make use of it. It is not at all the same thing as relinquishing ownership, which that Martian officer would not be able to do in any case because he didn't own the ship. The reasonable expectation is that they use the ship to do the job they needed it for, and then return it to it's proper owners.
This is, of course, only the second worst case of piracy thinly disguised as salvage in the Expanse. The title for the worst case of course goes for Behemoth.
I mean "the most wrong" as in that the TV version of her does not really fit into the general setting and story of the books, IMHO. She's really central to much of the story, but to me the TV version of her feels way to generic and Americanised.
Honestly, the only thing that I felt as being off was how they portrayed Earth as being overpopulated. If there were multiple planets/settlements to move to, and an increased overall HDI, you would expect there to be less people on Earth just due to shifting demographic trends. But, other than that it seems really realistic.