Who's your Most favourite 'Bad' Character in a drama you've watched?

Seo Na Yoon in Protect The Boss and Harry in Missing You.I just can't hate them.

My favorites are Ma Joon in King of Baking, Harry in  Missing You, Yoon in Warrior Baek Dong Soo and Gwi in Scholar Who Walks the Night.

Gwi From Scholar Who Walks the Night and Jung Seon Ho From I Remember You

The serial killer (I don't want to give spoilers) from The Girl Who Sees Scents. This guy had his shit together. I was filled with compassion after understand why he was that way and did what he did. And his abs... oh my. As some say, is almost insane how much fanservice they give for a murderer.

In Korean dramas: Well, the entire cast of Bad Guys was awesome! And, even though I wasn't the biggest fan of the drama The Devil (Korean version) Joo Ji Hoon's character was great.

I haven't watched so many dramas with bad or evil characters but there are one.
Yoo Yeon Seok as Baek Joong Chan in the drama Soul... woah he really captured the feel of a psychopath such a disturbed and well played character.

Here's a link to the drama if anyone want's to check it out :)
http://mydramalist.com/725-soul

Harry Borrison in "I Miss You" 

Without a doubt it was John Mayer in King 2 Hearts.  He was so sadistic and cunning in his interactions with every character in the show.