Can anyone recommend a drama where the protagonist is bad or turns bad during the course of the show. I'm tired of watching the typical drama where the protagonist is always good and the antagonist is always bad.

An example of this would be something along the lines of Bridal Mask (Korean), Ouroboros (Japanese), Chuno (Korean), Innocent Man (Korean), IRIS 2 (Korean), Maou (Japanese), Shark (Korean), Bad Guy (Korean), just to name a few. As you have seen it doesn't have to be the typical action drama.

Maou is the remake of korean The Devil.

Are you looking for anti-hero or evil protagonist? I'm asking because Ouroboros and Chuno fall into anti-hero category, if you are looking for evil protagonist though there is a movie The Unjust that covers just that. Gaiji Keisatsu also has a very questionable protagonist. There is also For the Emperor where nobody is particularly good (mature content alert) and Days Of Wrath where the protagonist from good turns out severely screwed in the head.
@Juls yeah ive heard about the devil, but i wanna give it sometime before i watch it since maou is still fresh in my head. and im looking for either, as long as they do things that are considered bad. also thanks for the movie recommendations.

@femmedesneiges i actually started that show and its a bit weird. i usually have no problem with that since i like weird its just the main characters acting isnt consistent. sometimes he plays it off well other times he doesnt.
White Christmas' plot deals with the line between good and evil so all of the characters would apply to some degree.
Salaryman has character(s) that go dark(er?) at one point and so does Can You Hear My Heart
You might check out Punch, Que Sera Sera, A Million Stars Falling from the Sky and Time Between Dog and Wolf. All of the protagonists are morally compromised in different ways, but they are similar in feel to the shows you mentioned. And I do highly recommend The Devil, although you might want to wait a bit if you just watched Maou.
Miss Ripley and Ouroboros. 
I recently finished watching Kurokouchi. I think the main lead fits what you are looking for
thanks for the recommendations, there are some i havent heard of yet on the lists! ill definitely check them out but in the meantime more recomendations are welcome. of course if you need some too ill be glad to help.