TLDR: Jasnah bears a greater resemblance to Meridas Amaram than she does to anything resembling a hero, and her father was wise trying to pair them.
Ever since WaT I have been forced to reevaluate my opinions of Jasnah. She went from being pragmatic with a hard edge to one of the most morally repugnant characters in the Stormlight Archive, and comparing her to a hero is inarguably laughable.
Given how little we have seen PoVs from her I intend to base this off of a few key moments to highlight Jasnah's sickening lack of morality.
Going in mostly chronological order the first thing that comes to mind was hiring an assassin to kill Aesudan. Early on this was played for mystery and suspense, but the reveal in WaT that Jasnah was just scared of her own sister-in-law really speaks volumes. When it comes to inconvenient people, even those in her own family, Jasnah's answer is murder. Not speaking to them, not patience, not understanding and compromise, murder.
Some might bring up Jasnah killing the footpads in WoK next, but I actually have no problems with that. What I actually wanted to look at was Jasnah's interactions with Renarin in OB. When she found out that Renarin had predicted the Everstorm Jasnah begins to watch him. Unto itself, that isn't too unusual or noteworthy, and honestly, some of the others should have done the same. However, when she confirmed that Renarin was bonded to a corrupted spren Jasnah's first response was to try and kill him. We can confirm this as we have Renarin's PoV from this encounter, Jasnah hadn't even spoken to him about this earlier.
I don't think Brandon took the time in the book to go over just how evil that actually is. She didn't ask Renarin for an explanation, didn't ask if he was hurt or in danger, nothing. For her it was as simple as: Renarin has a corrupted spren, therefore I should kill him. If Renarin hadn't looked at her at that moment I fully believe that she would have done it, which Renarin's visions confirm.
The final straw, and what finally got me to realize this pattern was the debate in WaT, when we found out the truth about Aesudan as well as Jasnah's plans to assassinate Fen as well as other coalition leaders. This was the ultimate confirmation to me, Jasnah doesn't have friends, merely useful tools. She doesn't believe in allies, just people who have the same enemies. Well is she labeled a heretic because to her nothing is sacred, and nothing is off limits.
Many have compared Jasnah to Taravangian, including myself. However, lately I have come to disagree. Taravangian cares about the people around him. He has friends and allies that he takes care of even to the point of creating a massive weakness for himself to do so. Jasnah on the other hand only cares for herself and her goals. She might care about her family, but to her they are replaceable, something that can be thrown aside if they become inconvenient. She is far closer to Meridas Amaram, and Moash. Jasnah is easily one of the most morally reprehensible characters in the Stormlight Archive and I hope she gets brought to Justice.