Lets start with the good things
1) Everybody would love the story setup as the Revenge company employees are just much better than normal people.(skill wise i.e. nothing much bad happens as the revenge employees are kind of like overpowered)
2)Music, Ost where just hitting the spot, loved the theme music sooo much.
3)Story's inspired by real life cases or crime's.
4)Action was on par with movie quality.
5)Supporting cast( victims and assailants from all the different stories) where 10 /10.

Now the disappointing points
1)The main lead had nothing much acting to do as I felt they where always getting rushed to taking revenge.
2)Kang Ha Na(Esom) this character felt like it was not part of the drama until second half, I feel this drama could have done better without this character.
3)At the end of episodes there was small segment showing connections between all the characters in the story. But the problem was I had forgotten about few of those characters was this a failure of my memory or failure of the drama to make me remember their stories not sure(I watched it when it aired, may not face this problem when binging)
4)Kim Do Gi (Lee Je Hoon) was practically a superman, no military training can make someone that strong. Because of this Taxi Driver became from real life fiction to supernatural fiction vibe. I mean it didn't feel real.

Conclusion
Watch this show it would give you a warm feeling at the end and there is no bullshit about moral value , forgive your enemies etc.. This show is for all those who are sick and tired of watching over the top good characters who forgive everyone.