Florin Scanlon’s review published on Letterboxd:
I guess people do change. Or at least their taste in movies. Before this rewatch I Saw the Devil was a five-star movie. It might not look like a big jump in terms of ratings but changing from an all-time favorite to a mildly passable watch, there's quite a gap to come to terms with. There was a time, not that long ago, when I Saw the Devil seemed like a completely riveting and deeply moving experience, a visually enthralling morality play and of course, a super awesome, brutal and thrilling revenge flick. Now, it's anything but.
One of the most egregious aspects of the film that provoked such a turn is the film's often shifting tone, which muddles the emotional and visceral effects it strives to produce. At times playing like a tragic tale of loss and a desperate attempt to cope with said loss, there are other times when the movie slips into pure action-y shenanigans that feel strongly out of place. Very competently staged on their own, these tonally contradictory moods don't mesh well together, with one frequently undermining the other. This is most evident in the score and the camera work. Scenes containing beautiful and sad classical music are followed by scenes with your typical, alert 90s action sound. Restrained camera movements that accompany quiet moments are ditched when the next action scene arrives in favor of crazy spins and angles, which are very cool but don't really fit with the rest of the movie.
Then there's the excessive indulgence in violence and the exasperating repetitive nature of the catch-and-release plot structure. The violence is taken to an extreme in an attempt to enhance the gravity of the story of a man who lost his loved one. It also supports the point that evil is very real and even the good and just can turn into monsters, given the right push. However, this is hardly sufficient to justify the graphic violence, which instead seems to be an exercise to see how far one can go. There must be better ways to show the sadness in a soul being mutilated and transformed by pain than actual physical mutilation and pain. Near the beginning of the movie, a beheaded head is dropped from a box and rolls on the ground to the feet of our main character; that's as cheap and sensational for the sake of being sensational as it can get. As for the repetition, it makes the already long film drag to a point where it greatly affects the viewing experience.
The character played by Choi Min-sik is evil personified, which in a way is refreshing as so many villains are described as either having ulterior motives or some sort of goodness in them. He really is a disgusting and atrocious human being without any redeeming qualities who doesn't need a reason to be evil. He is over the top and one-note but that's a conscious decision which seems appropriate, as Choi Min-sik's intense performance elevates the character to an almost otherworldly, unstoppable force (like, the Devil). Yet that doesn't excuse the movie from giving this character terrible lines of dialogue. When it comes to the themes of the movie (good vs. evil vs. pain, the poisonous impact loss can have, the futility of revenge, becoming the monster you try to destroy, moral ambiguity), they are interesting but not as interestingly explored. Even though it takes itself very seriously, the movie doesn't go very deep and there's not much meaning that can be extracted from it.
There still are a few positive aspects that remain even after this rewatch. The cinematography is great, there is variety when it comes to the settings, the action sequences are well choreographed, the brutality of the violence occasionally works in the film's favor, the acting from Lee Byung-hun and Choi Min-sik is spot on, and the movie still retains some of its emotional impact (the last scene remains a superb example of powerful film-making). But the excessiveness, the self-indulgence, the jumbled tones and the fact that the movie doesn't amount to much beyond a shallow action thriller disguised as a deep meditation on the evil that is present in the human spirit brings I Saw the Devil down crashing. I used to fucking love this movie.