This had been in my queue for some time, as the capsule description wasn't particularly compelling to me. After watching it, I realized there was no reason to have hesitated.
Overall, a strong crime/corruption/revenge k-drama leavened with a good bit of action and a bit of romance.
If you watch many k-dramas, you will recognize a number of cast members, all of whom turn in good, or at least serviceable, performances. Good cast chemistry.
I noticed a couple of reviewers comment about Min-su Choi's performance with his guttural delivery at times. While I do think he may have slightly hammed it up a little with this, and with his physical acting (his gait for example), I thought it was just fine and not over the top for his gangster character.
My main criticism is around the pacing. As I often notice in k-dramas, it can lag a bit in the middle bits. I also felt the wrap-up was needlessly hurried. They could have easily written the events of the final episode to unfold over two or maybe even three episodes while tightening up a few of the episodes in the middle.
A secondary criticism is that I think the some of the writing around various plot development slightly strains credulity, but by the standards of the genre, in which entire stories often hinge on the most improbable of coincidences, this is a pretty minor point.