I knew D.O. mainly as a singer, but he is also a good actor.
The plot leads his character, a champion of justice, to act as a "phenomenon" in an exaggerated way.
He and his team are in danger but always work separately?!?
The big bad boss played his cards face up, it would have been simple to touch a button on the phone and record conversations. So they would have had a thousand evidences.
Why are the fair people so stupid?
This point makes me lower my rating.
The last 2 episodes were honestly the worst two, where I got the most anger.
He knows full well the power of the old bastard and how cruel and unrepentant he can be for his actions.
I wondered why he was so naive as to come up with these brilliant plans where he gets beaten up, people close to him get involved and he is blackmailed, he has the evidence and has it stolen and last but not least, he has to ask for help from that "change flag" of a prosecutor.

All's well that ends well. Fortunately in the end he redeems himself and we understand that he wasn't that stupid.

PS: His team's hacker, Lee Si Eon, had the same role as in the "Player" series.