A good villain makes a good movie/drama and bad one totally ruin it for me. I like when the movie/drama has this handsome, charming and amazing villain that you could even like more than the hero.I'd like to know about movies where the villain gets the spot light (very cool, has love interest, his actions can be justified some how,..etc). 
Some examples:
Cold Eyes
Monster
Oldboy
Confession of Murder

EDIT: I forgot to mention anti-hero....You can also suggest movies/drama starring anti-hero
great villain??
you need to try ongoing drama
Missing Nine and
Defender
both anti's is going to make anyone mad!
Gap Dong~ best villain ever!
Zeni Geba - it's a japanese drama, but the main character is actually the villain, so you might be interested in it! I just loved this drama because of him~ he's such a complex character!
Awesome Villian: Mask & Scholar Who Walks the Night
Anti-heroes: Bad Guys & Ouroboros (J-Drama, but I think you'll really like it)
phantom ( K-drama ) bloody monday (J-drama )
I will also recommend 'I Remember you'
Thanks for your suggestion guys! I'm keeping an eye on all of them, I was hoping for more suggestions of movies because I feel too lazy to start a new drama and commit to it :P anyway "Gap Dong" seems interesting enough so I'll give it a try