Joo Dan-tae (Um Ki-joon) (The Penthouse: War in Life, all three seasons)

Lady Park from Matchmakers. I love a good villain with well-fleshed-out motivations you can understand, and even empathize with.

Lady Mishil from Queen Seondeok.

There is no villain that smexy that makes me watch the entire drama, but there are villains that send a shiver down my spine everytime they are on screen. It's Jung Hyunsoo in Suspicious Partner and Min Joongook in I hear your voice.

Jayden Lee in Doctor Lawyer
I don't know if this counts Lee Rang in TONT

Park Hee-soon in My Name is the smexy villain who you wind up watching the entire drama for. He was the only reason to watch My Name.

The last villain to leave me breathless with awe and angst was Park Sung Woong in Bloodhounds. He completely embodied that evil character. He was relentless and scary!

Lee Chung-ah in My Dearest was SO, SO ANNOYING. I literally wanted to strangle her, and I haven't felt like that about a character in a long while... so I guess she did her job well.

Jeong Bo-seok - Giant
- Probably the greatest Kdrama villian of all time

Other great ones:
Kim Joo Young - Sky Castle
Baek Hee Sung - Flower of Evil
Mo Tae Gu - Voice 1
Lee Jung-hye - Perfect Marriage Revenge

Jo Yeo Jeong when she plays an intense, scary and dangerous woman. In MS. PERFECT she discretely played a friendly sociopath to perfection. In BABYSITTER, she is a humiliated wife of an adulterer whose calm mental state masks a scary rage for revenge. Even in CHEAT ON ME IF YOU CAN, her demeanor was like a cold blood killer staring you in the eyes. In all three shows, her character was completely different but the vibe was the same.

Lee Hyuk in The Last Empress. The villain who stole my kdramaheart.

Mishil from Queen Seondeok remains my hands-down pick in this category, although other favorites include Jo Pil Yun (Jeong Bo Seok) in Giant and Oh Seung Ha (Joo Ji Hoon) in The Devil. Without giving spoilers I'll also say that Forest of Secrets season 1 and Pied Piper have exceptionally nuanced and well-acted villains as well.

Haechi managed to make me feel sorry for the villian! It also had me unsure if a villainous character was, in fact, villainous. It made for a really interesting watch. Then there are all the k-drama bad boys that end up sweet at the end (Boys Over Flowers archetype). They are often pretty villainous at the start.

Ooh, now this is a fun topic!

Ahn Oh Joo (Choi Min Soo) on Lawless Lawyer is one of my all time faves. His character is so campy and fun with his 70’s Vegas lounge singer vibe.

And then there is Jeong Seo Min (Song Ha Yoon) from Marry My Husband whose self delusion and manipulation is so well hidden under that act of innocence that she’s scary!

Lee Dong Gun's Yeonsangun in Queen for Seven Days

Kim Yeong Chul's Prince Suyang in The Princess Man

Jang Hyuk's Yi Bang Won in The Country: The New Age. Was he even the villain?

Kim Bum's Lee Rang in Tale of the Nine Tailed - I just cant hate him even if be does whatever to his brother.

Hands down, Shin Sung Rok in You From Another Star. Because I was literally scared of him there, which I think did not happen with any other villain in a K-drama for me, ever. Yes, there are flat and boring villains, cartoonish villains, so-annoying/eeevil-that-you-want-to-rip their-head-out villains, smexy villains, sympathetic and/or nuanced villains, and my second favorite type: the almost-antihero, Loki-like villains (often overlapping with the smexy category), but none of those ever made me want to hide behind my pillow while watching. P.S. Second place: Lady Park from the Matchmakers, because that was the most nuanced and true-to-life villain persona I have ever seen in a drama.

I don't like plain villains, so this is a difficult question.

I'd say Mishil (Queen Seon Deok) because her charisma was outstanding.

Is Baek Yi Hyun (Yoon Shi Yoon) in The Nokdu Flower a villain? I'm not sure yet. But it was an easily hateable character. His evolution was really painful to watch.

Very different cases are the funny characters played by Son Ho Jun in My Secret Terrius or Lee Jun Ho in Chief Kim.

And the character played by Park Hoon in Memories of The Alhambra was so creepy.

Thinking about Chinese dramas, Joy of Life has some great villains.

Mishil (Go Hyun-jung) in Queen Seondeok. Every moment of watching her sashay on the screen was either a learning moment for me or me just stunned to silence at the way she exercised herself in the Shilla court.

I love a villain who knows how to count their losses, take a win, take a loss, and most importantly, teach the protagonist something in the art of war. Mishil fulfilled all these categories to the perfect sense - dotting her i's and crossing her t's. There was no dulling moment with Mishil.

Honorable Mentions

Won Sang-ah(Uhm Ji-won) and Park Jae-sang(Uhm Ki-joon) in Little Women. They are also my favorite villain couple.
Shin Sung-ruk : You From Another Star, The King's Face.
I'll have to dedicate a paragraph to this honorable mention...
Jung Nan-jung (Park Joo-mi) in The Flower in Prison. Something sets her in the same rank as Lady Park in The Matchmakers, another villain worth mentioning, yet sets her distinct from Lady Park. While Lady Park had to step into the spotlight as the story unfolded, Jung Nan-jung was always in the spotlight. Never in the background, but ever spearheading the affairs of her clan in broad daylight. So distinguished Jung Nan-jung is, her name is etched in Korean history as one of the prominent women, ranked alongside politically active queens and empresses of Goryeo and Joseon.

Lady Park in the Matchmakers> Because she was a nuanced villain. She had good sides like her love for her family and bad sides like her ambition.

Choi Min-Soo in any drama like Warrior Baek Dong-so or Numbers> He's so charismatic!

Eugene Han in Money Game> Again, this character was nuanced and Yoo Teo did a good job in this role.

??? in Nothing to Loose> It was surprising.

Yoon Hyun-Moo in Come and Hug Me> He had a redemption arc and Kim Kyung-nam stole the show in this role.

it's still Ki Cheol from Faith!

A delicious thread! I always felt kdrama is not so good with villains, tending toward caricature and the overly obvious, but there are some standouts. Lee Dong-gun in Queen for Seven Days made me think he wasted his time playing nice guys. Lee Sung-min in Reborn Rich. Kim Min-jung was a fun villain in My Fellow Citizens.

Oh So Min was a truly evil villian. I don't even know what to say about her cause to give compliments feels weird but the actress did such a good job with her.

I honestly feel like she would still be trying to ruin Ji Won's life from prison as well as possible have a hit put on her (in the world beyond the drama).

Min Hwan is also unbelievably disgusting. Again, another good performance and it's weird to compliment him.

It's been a long time but over the years no other drama villain has ever taken my fancy like Ji Se-kwang in Incarnation of Money. Park Sang-min came close to stealing the drama. One blogger started calling it the "Park Sang-min show."

Tagon from Arthdal Chronicles. His story was just so interesting to watch, from his rise as a villain in S1, to his reign and eventual downfall in S2. I think he's just a well-written character in general. He's calculating, and pretty smart I think. He managed to completely fool me in S2 when I thought he'd gone mad, when in reality that was just one of his crazy plans. Even his final desperate plan in S2 was actually pretty smart, and he probably would've succeeded if it wasn't for Taealha coming in to make a deal at the last second. I hate him, but I also love him. Speaking of Taealha, she's an excellent villain too.

Cha Yool-moo played by Kang Tae-oh in THE TALE OF NOKDU.

I think the reason why Yool-moo’s villiany lives rent free in my head, is that I watched this drama after a certain (non-kdrama) ship penetrated the mainstream and I was baffled by its popularity. Look yeah I’m normally a ‘ship and let ship’ kinda person but Yool-moo was such a great deconstruction of the “I can fix him” or “love can cure him” or “he’s just misunderstood and he’s not that bad” type of rational.

(Copying and pasting my previous comment which pretty much sums up my thoughts about Yool-moo)

TALE OF NOKDU not only showed the horrors of unrequited love/abuse from a man who couldn’t take no for an answer, but the drama also didn’t put the onus or burden on the FL Dong-ju to change him. The fact his “love” was never going to override his power hungry ambitions was the whole point.

I don't count these my favorite villains because I don't fall for villains, especially when they are too powerful, and I'd sure never finish a show for a villain. But there have been many villainous characters who have been memorable for one reason or other.

How many villains did Connection have? It was basically a villain ensemble, every single one (minus one) amazingly drawn and acted.

Park Hoo Ja in My Fellow Citizens because she was so dumb but thought she was so smart! 😂

Seo In Woo in Psychopath Diary because of how hilariously he was mistaken at every turn! 😂

Noona in King the Land because she was so understandable she could be the hero of her own story.

Baek Sang Ho in Nobody Knows because the audacity of that man.

Jun because he is too good at it, dammit.

The other ones are spoilers 😄😄