dubious/morally grey FL

Get Karl! Oh Soo Jung she's a gold digger, no excuse for her. But she gets some character growth through the drama. Old drama though!

I Have a Lover she's a villain. She's greed and ambition personified. A lot of growth for her. 

So Wayree usually in dramas, the FL is misunderstood by the ML who starts treating her like shit before realizing he was mistaken, and then he starts being nice? That, but in reverse. She puts the guy through the ringer for a long time before she starts to come around. (Although this is an unpopular opinion, as some people feel like he deserved the treatment). 

Some of these might work for you:

Blood Free (FL has no idea whether she's good or evil. Opinions vary.)
The Witch's Diner (FL does naughty thing, then not so smart things.)
Hyena (You don't get more morally grey than this.)
Hotel del Luna (FL is not too concerned about doing penance for her many, many sins. But, damn, the eye candy in this thing!)
Doctor X (Fights the power by projecting a massive god complex of her own.)
 I Hear Your Voice (FL is incompetent, selfish, and altogether not very nice. Got so fed up with her that I dropped it.)

• The Blue Whisper: Part 1 - She does bad things and works for bad people and has questionable morals but is ultimately righteous Kidnapping, manipulation, torture, traitor
• Dong Lan Xue - Questionable morals and a thirst for revenge the killing type
• Lie After Lie - Questionable morals and actions but with honourable reasons stalking, lying, manipulation
• Wake up to Fantasy - Ruthless and cruel kinda implied that she was pretending? but she still did p nasty shit
• Monster Hunt - More comedic but yeah Cruel and heartless
• Secret of Three Kingdoms - Questionable morals and actions but with honourable reasons Careless of people's lives, cruel and heartless
• Kingdom: Ashin of the North Ruthless and cruel with reasons Vengeful, starting a zombie apocalypse, mass genocide
• Vigilante  - Unhinged with questionable morals Very pro-vigilantism, unhinged
• Evol - Unhinged with questionable morals along the lines of 'maybe being evil isn't bad'
• My Name - Questionable morals and a thirst for revenge murder, manipulation, lying, betraying
• Beyond the Dream - Questionable morals due to trauma abuse of power, romantically taking advantage of a disadvantaged person
• Ye Cheng Fu - 'righteous' to the point it 360s back. Abusive towards her love interest and generally not a good person  
• Rise from the Ashes - Revenge driven but ultimately righteous
• + Hotel del Luna

Villain FLs: 

• Kyouso no Musume - Psychopath 
• The Legend of Zhuohua (SFL)
• The Blue Whisper: Part 2 (SFL)
• A Familiar Stranger (SFL)