The best parts of this drama are:
1. The plot is so solid. This drama doesn't waste your time with over-crying, over-kissing, etc. It really provides you a pure story. Every episode WON'T let you get bored.
2. Every episode will make you laugh. Yes, although it's crime/thriller/action, but this drama is also a comedy. The director twists so many scenes that—I believe—will make you laugh.
3. NO shitty useless romance scene. Unlike other drama, this drama doesn't have 'romance' things. So, the 16 episodes really give you different feels. It's only between laugh or nerves, no lovey-dovey waiting for the actor & actress to kiss.
4. The acting of the actors and actresses are so damn good! The main actor really acts like a stupid guy, and he acts like a psychopath seamlessly. You know, it's so hard to play two roles in one character. The main actress shows her emotions very well. She doesn't need to over-cry to express her sadness. Instead, she shows her meaningful expression through her beautiful face.
5. Haven't come to my mind, I'll add them to here once I remember.