Any of you ever read Cultivation Nerd? On SB and RR. I've been following along with it since pretty early on, but it wasn't quite interesting enough for me to say anything about until now.
Starts off with transmigrator MC, member of an okay-sized local clan that is pretty mid compared to the sect they feed into. Guy he transmigrated into just got his shit rocked in an outer sect tournament. He was kind of arrogant but hadn't made any enemies yet, so no real baggage to deal with. MC is not an ambitious guy and mostly just ends up hanging around the library. He just wants to eventually reach Foundation Establishment to not be pushed around so much and can just peacefully read books. Between that and the mediocre talent of his body it seems set up to be a low-key MC. Particularly since there's a more obvious typical xianxia MC type running around as well with his grandpa in a ring and whatnot.
Things change however once he starts getting into the action, and with the backer he attaches himself to. While his cultivation speed isn't (too shocking) owing to the mediocre spiritual roots, his comprehension ability is certainly quite talented, and his fighting ability is no joke either. He also ends up becoming the lackey of a "young mistress" type, daughter of a major clan head, and niece of the sect leader. Very talented, very perceptive, but also very violent and direct. Somehow MC endears himself to her with his no shits given attitude, giving things to her straight instead of bullshitting her or sucking up like other people. Story seemed like it was going in the direction of him becoming her lieutenant and the brains of the operation, and perhaps making her less psychotic over time as he reigns her in.
Instead, as events have progressed, she's gotten worse, and seems to have made him worse too. She's become even more murderously psychopathic and MC has become way too comfortable with her spontaneous murders. But the two have this strange inexplicable trust with each other. For an example, when MC was badly injured and she brought him to her clan's medicine hall they put him in queue because they were treating a family member. So she just killed that injured family member on the spot and made them heal the MC instead. Or when the MC was visiting her in prison after that (where she was being tortured), and being escorted there by a gold core (he's in like qi refinement), instead of saying what the gold core wanted to hear, like trying to reason with her or talk her down from doing something else stupid, he instead told her they should just tear everything down and destroy it all after she gets out of prison, right next to that gold core that could hear him.
One commenter described MC as becoming the strangely rational and affable second in command to her psychotic evil dark lord type. Kind of an interesting dynamic. Morbidly curious to see where this goes.