As I'm reading other reviews, I'm realizing we all kind of had the same off moments.

I don't want to repeat what has already been said but this drama truly had some great potential at first.
The bromance is very nice, the highlight of the show. WDH showed everyone some heart in all he did which was very inspiring, yet unrealistic at some point. The fighting scenes were very impressive even though I can't tell how normal it can be: 2-3 men taking on 30 men. Also episode 4, the car chase was literally so good. That truly got me shivering. Let's not forget the effects creating the wounded bodies, the blood and everything else. Such a good job!

Indeed there were many plot holes. So they were fighting this really bad guy but they also did not add to their security or safety after having attacked the bad guy. Instead they just went back to their normal day and routines and that was really off.
The first 6 episodes built the whole history while the last two were just a bad speeded wrap up. Some things felt forced just to end the show. Tbh I thought there was gonna be a 2nd season, considering how good they were trying to built the story at first.
They had the chance to bring Kim Hyeon Joo back for the final attack, but instead they added Oh Da Min to the fighting team. The moment she heard about her grandpa being kidnapped, there wasn't a single emotion expressed through her face.

To sum this up, this drama made me experience some very strong emotions; it had the power to captivate me and make me binge watch 6 episodes in just a day. It's a solid 8 I would say. You can totally give it a go. You'll get some good visuals of Kim Geon Woo :p