DirkH’s review published on Letterboxd:
Ok, let's get the OldBoy comparison out of the way first. OldBoy is plot driven, I saw the Devil is driven by intense visuals. The only thing they have in common is that they have the same lead actor and deal with the same topic: Revenge.
So, that's that, the comparison ends there for me. I saw the devil is a horrible film and I mean that in a good way. This film has the ability to make you look away in disgust. I have a rather high threshold, but I caught myself looking away at more than one occasion. Gore is often numbing, but not in this film. The make up effects are extraordinary. The realism combined with the excellent acting make this film a harrowing experience at times.
I saw the Devil explores the limits of sanity and gives pure evil a face. The plot is wafer thin, superfluous even. But that's okay, its merits lie elsewhere, namely with the director and its two leads.
Kim doesn't want to ease you into this film, he makes clear what he wants from the get-go. He wants you to feel uncomfortable and he really succeeds. He has a great visual flair and is very good at sucking viewers into the action and thus making the violence all the more intense. There are scenes in this that will stay with you for a long time (particularly a scene in a taxi cab, which is just phenomenal).
The two leads are fantastic but, credit where credit's due, Choi's performance as the evil as hell serial killer is something else. He is feral, without conscience and incredibly violent, an astonishing performance.
Yet another well deserved entry into the ever growing Korean revenge classics!