Kim Wo Bin is always an inducement to try seeing it so here I am. I really loved the first half of this, it's actually funny and I was positively giddy whenever he went out to stop one of those monsters, but the last act is typically over the top suspension of disbelief kind of thing. In addition to the fact that it suddenly shows the monitoring unit being very unprofessional and making mistakes in succession it shows the guy going full rogue by himself with his silly entourage of friends and actually getting away with it and being commended for it.
First of all why would such a dangerous criminal be allowed to walk outside when the others were not? So he is allowed to go eat outside, they just leave it at that, they're being polite even. Then how can they be so stupid as to be ambushed like that? Then why does our guy go in pursuit of the criminal without his anti-stab vest? It's official police business so he should be wearing the vest. How could there not be an investigation after those casualties?
Then at the end when he becomes a vigilante, how stupid can you be to believe you can take on a guy like that and all his entourage? It's a numbers game. Well, Korean movies do that all the time, but this started out by presenting this police unit in a very positive light so why not do it with them? Why not call for backup when he was in danger, notify them of the criminal's position at least. He could have easily gotten away. Makes no logical sense, other than that the purpose was to create full-on action scenes and make the movie climax using that, never mind the law and logic.
It's half very entertaining, half stupid, but still entertaining if you're willing to forget about it being incredibly stupid.
