Beautiful visuals are probably the only positive aspect of this show.

The main issue is the subpar writing - basically just haphazardly stitched together tropes with abundance of melodrama. The intention, i think, was some sort of star-crossed lovers & with bad-boy-saved-by-love story, the result makes cheap day-time telenovelas seem like quality tv.
Honestly, the only criteria for the plot seemed to be over-the-top angst and the absence of logic. The emperor? The scared brother with parental issues? The amount of torment dished out to ML? And what about the clothing - if you make a storyline about ML not having warm clothing in winter, can´t you let everybody wear warm clothes? How am I to take it seriously when half the cast is in chiffon?? And for godsake, can´t you let them sleep without the ridiculous headpieces? (I know this one is truly silly, but given the overall problems, it irked me so much).
The FL in the first few episodes is painfully stupid, her decisions driven by nothing else but topping up the already exaggerated situation (example: XY explains what has to happen and how she needs to go and do this and that, FL says ok and stops and watches bad things happen so you can have here cry and shout uselessly - otherwise we would not get that this is a severe problem, oh no, just world ending, without the crying heroine, how would i know?!). And then suddenly she turns into the perfect actress - and competent fighter and responsible member of society without any issue despite the fact till that point she was a spoiled idiotic villainess.

All (main couple included) the characters are paper-thin stick figurines, driven by the magical plot-said-so-shut-up without any personality, stable traits or logical motivation. A scene to scene their behaviour changes for no good reason aside from what sort of trope the scene had to convey.
The show tried to cover up the lack of care for the characters by the tragedy and melodrama and... a sense of forbidden fruit, i guess (psychopathic male lead, the steamy scenes - ah, another plus, the kissing scenes are realistic not the usual barbie dolls), but it´s not enough - definitely not for this type of show. Instead of taking time to develop them, to make me as a viewer care about the story and its inhabitants, they just rushed to epic fights and emotionally hightened moments (where the stakes are so high, it´s almost laughable) for a momentary entertainement but without any substance. (I think i would enjoy it more, if the ML stayed evil and just went around murdering anybody).

The subpar writing is probably a reason why the acting seemed... less than idea (ML switching from besotted to trademark evil to constipated to blank model face randomly; a character talking suddenly in deep voice and being all powerful and suave just because she turned evil). But i will admit the choice for the ML was great - the actor looks like tragical heroine suffering from consumption with just the right amount of decadence, so at least they had that going for them.
As for the main couple - yes, their chemistry is nice to watch, as long as you forgot the ridiculous plot (the weriters surely seemed to - early happy frolling in the snow and then hurray, our main guy is emotionless psychopath again) and take them as generic FL and ML in tropey situations.

Can be used as background show for the pretty visuals and brainless nonsense.

Or even better - if you enjoy xianxia and are deseprate for something good, go watch Love between fairy and the devil, this one is really waste of time. (Did they make LBFD as an angry response to this drivel? It does sound like that.)