She was also very good at being a teacher and disliked both Jedi and Sith for entirely legitimate reasons, and given how KotOR2 ends, canonically the Jedi Order we see in the movies is founded at least partially on her philosophies (going by Legends canon).The mentor figure from KotOR2. Her main trait was telling you that you were wrong and an idiot, no matter what you did. Many of her students became Sith, she was herself only sort of Sith but was called "Darth Traya" so take that qualification with a grain of salt. She was not a fan of the force and wanted to try to kill it.
This does not detract from the fact she is also a huge jerk, but anecdotally, keep in mind that Kreia revealing herself to be Darth Traya takes one of two ways depending on if the Exile (the main character) is Light or Dark Side. If Light side, she reveals her true Sith capabilities as a consequence of saving the Exile from the surviving Jedi Masters, as they reveal they don't care that the Exile has been a frankly good person, only that she (the Exile is canonically female) is a wound in the Force, and kinda maybe sorta possibly will become a threat if she follows Darth Nihilus' example and becomes a Force vampire (keep in mind the Exile killed Nihilus and was only able to due to being a wound in the Force able to drain his powers, and that your party has become heroic badasses because the Exile forms Force bonds as easily as she breathes due to the same reason), so they're going to remove her ability to perceive the Force all over and send her to an even worse hellhole then she was in at the start of the game. Only in the case of the Dark Side does she actively betray and try to kill the Exile - because she's been such a horrible person that she's proved the Jedi's point, that a wound in the Force can only leave suffering and death in its wake, and besides, the Dark Exile is also really Stupid Evil, which she haaaates. Also that she, mechanically, forgives Light Sided violations of her philosophy a lot more readily than Dark Sided ones.
EDIT: Though taking anything Kreia says with a grain of salt is a good idea; she's perhaps the best liar in the Star Wars universe.