Regarding season 1, I liked the earlier episodes and I was looking forward to the upcoming ones but things didn't go as expected. They had a really poor mix of investigators and journalists/reporters working on the case. Not even the involved characters from that side were appealing to watch. You often hear in any police/investigation drama how they keep information away from journalists/reporters to not hinder the investigation, it turned out they were right. I liked how Oh Ji Hyuk didn't stand out as a main lead too much to allow those around him to have a space, he blended in nicely. Him and Do Chang had a nice dynamic but they started to drift apart a little bit later on.
Compared to season 1, the main case was definitely less interesting. The involved parties were boring. The investigation was slower and much simpler. There was barely any tension, not much action and thriller anymore. Most of the time they were slacking around. Less budget maybe? Throughout both season there was a very small side plot in the background regarding Oh Ji Hyuk and finding a meaning in living but the writer didn't allow for such development and, eventually, after 2 full seasons, everything boiled down that he found a meaning in life through being a workaholic detective. The way they handled that after 32 episodes was the most disappointing thing about the whole thing.