A story line that keeps you at your toes at the end of almost every episode, this is an action packed thriller that I cannot believed I missed during its airing. I admit I first started watching this drama for Park Hae Jin but I left this drama having a greater appreciation for not just him but the entire main cast and their amazing chemistry. This is a drama where all the cast members shine ---- each have a meaty backstory that reminds you these characters are not actors playing stereotypical roles but three dimensional people each with their own agenda however flawed it may be. Like the title suggests, this is a story about "bad" guys, people who walk a tight line between law and crime. I like how the story explores the boundary between what is right and wrong through its characters and questions whether they are truly "bad" as society condemns them to be. Acting here is phenomenal especially Kim Sang Joong who plays Oh Goo Tak, a morally ambiguous cop who would do just about anything to avenge his daughter. Even though it has only 11 episodes (shorter than most korean dramas I've watched), the director really manages to make every scene count. The drama is not perfect but it is one of the better dramas I've seen in a very long time. Definitely give it a go if you like thriller crime stories with an amazing cast and killer bromance.