Let's share our thoughts! :)

name of actress or actor

drama that made you ADMIRE or LOVE him/her the most

Please elaborate.

Example:

Kim Ji Won

Descendants of the Sun

Compared to her role in The Heirs, I was attached to her character in DOTS where her love story is what I admired more.

Lee Soo Hyuk

I hated him in High School King of Savvy.  I thought he was a terrible actor, like a robot.

Then I watched him in Scholar Who Walks the Night and realised that he was a really good actor.  His character Gwi was the ONLY thing i liked about that drama. but he still irritated me.  I still didn't like him

Then I watched Valid Love and totally fell for him.  I'll watch anything he's in.  I no longer think he acts like a robot, I think he's subtle
eita in Saikou no Rikon and then in wakamono tachi ... he depicted both roles in an amazing way ^^
Kong Hyo Jin
It's Okay That's Love


It was my first drama that i saw her. In the first few episodes, i feel she's not pretty enough to be Jo In Sung's leading lady, and she sometimes made weird choices on her wardrobe that made me cringed. But as the drama progressed, damn..i think she has such that kind of unexplainable aura..one of the coolest woman on earth.
panda - sugagagkoko scandal HAHAHA

me -

IU
the producers
very very pretty + very very difficult role but she was the best of that drama
Kong Hyo Jin

It's Okay, That's Love is the first drama I've seen her in, and I find her talented, but not attractive. But then, in The Master's Sun, she became my 'official' candy girl!!
Empress Ki 

When I saw Ji Chang Wook acting all needy and unattractive I thought "wow this is what real actors are like" one minute you can love their sexy character and the next minute you hate them. He's a really good actor.  
Right now i'm watching 120 episode family drama Sisters-in-law 
http://mydramalist.com/22679-sisters-in-law
it has two (old-timer) idols as leads
and they're gorgeous and very surprisingly good at acting
T-ara Eun Jung and After School Joo Yeon
http://mydramalist.com/profile/immortalcupcake/fee...

Always

Always is actually a movie starring So Ji Sub and Han Hyo Joo. I thought that So Ju Sub's acting was pretty flat both in Oh My Venus and the Master's Sun. I was very impressed with his role in Always. Han Hyo Joo moved to the top of my list of favorite female actresses. I think that she was phenomenal in her role. Her acting really brought the main character to live. 

I will also agree with That's Okay, It's Love. Kong Hyo Jin often gets cast in similar roles as an unlucky pure girl like in Pasta or the Master's Sun. I didn't think she could pull off a more sophisticated role. Tha'ts Okay, It's Love proved for me that she actually is pretty versatile. I'd like to see her cast in a crime drama now.
Kim Ji Won

"Descendants of The Sun" and "Fight For My Way"! Heck, her role in "Descendants of The Sun" together with Jin Goo was even more interesting than the main couple! And, I also really loved her role in "Fight For My Way"! Female leads are becoming more realistic by not being super cute/feminine. She was easy to relate to. :)
Park Hae Jin

I don't like him and I never understood this hype because he has less facial expression and doesn't transport any feeling with his acting.Then I saw Bad Guys - he was an amazing psychopath! I only watched Cheese in the Trap because it seemed like he will play a psychopath again (and because of Kim Go Eun). If he performs the evil or psychotic guy, I would go for that drama.
Didn't like Park Seo Joon in She Was Pretty, but loved him after Fight For My Way
Hated Park Hae Jin in Cheese in the Trap, liked him after My Love From Another Star
I loved Shin Sung Rok since YWCFTS, Lee El since Liar Game, and Ji Sung since KMHM. 

There have been other dramas that put a certain actor or actress on my radar, like Jun Ji Hyun in YWCFTS, Yook Sungjae in Who Are You - School 2015, and many many other I want to see more of now.

On the other hand, the opposite has sometimes happened too. I loved Yamapi in Nobuta wo Produce but not in anything I've seen him in after that.
Joo Won - I never have watched anything of him, then I watched Yong Pal a few weeks ago. Good acting. Then I watched Good Doctor. I truly respect him now. His acting skills were another level... maybe one of the best korean young actors I've ever seen.
Kim Young Kwan - first watched him on Pinocchio. Okay, didnt caught my attention. But, this year he totally slayed as the main lead in The Guardians. 
Go Kyung Pyo - I absolutely HATE him on Jealously Incarnate. Also wasn't my favorite on Reply 1988. Then I loved him on Chicago Typewritter... Currently watching Strongest Deliveryman because of him.