I loved this K-drama, and I learned a lot from it. I don't know why most people are not enjoying season 2 like they enjoyed season 1. Maybe it is because it focused less on the main characters (the revenge team's) backstories and more on the revenge. The series already covered their story in season 1, so they will not have a reason to show it again. Nonetheless, it was still very enjoyable, and the plot twist of a character not being who he truly is made me love it. Although Shin Jae Ha physically did not seem very much like a formidable villain, irrespective of that, he did play his role very well.
Also, I want to say that Mr. Kim Do Gi still needs to go to therapy; he might not be able to fully overcome his trauma, but he will be able to manage it. And I think we can all agree that Mr. Kim is superhuman because he is really doing some sh*t that normal humans can't do.
Anyway, kudos to the crew, cast, and everyone who contributed to the success of the series. I am happy I went against everyone's opinion and still went ahead and watched the series.