Wesley R. Ball’s review published on Letterboxd:
Wow. Just wow. Holy crap. That.... That was quite an experience unlike anything I've seen.
"I Saw the Devil" is an intense, atmospheric crime-horror film about a serial killer, and one cop's search for revenge when the killer murders his pregnant fiancée. It's unique in that, the majority of the film is actually shown from the killer's perspective, so we get to see all the nitty gritty details of his heinous deeds.
However, things really start to pick up when the revenge plot comes into play. The cop decides to play some mind games with the killer, letting him go several times rather than arresting or killing him. The murders in this film are reminiscent of the likes of John Doe from David Fincher's masterpiece "Se7en," and it certainly doesn't play down from its predecessor in any way.
The whole film has a beautiful color theme present in all its scenes that give it a very artistic feel, and that's one thing I love about a movie. Films like Drive and John Wick also have their own intricate color schemes present, and "I Saw the Devil" is no exception from this. It really is beautiful to see.
Violent, thrilling, and intense all at once, "I Saw the Devil" is one of the most beautiful horror films I've ever seen. This film has proven to me that "Magnet" can in fact release fantastic films, perhaps I will try looking through their offerings on Netflix at a later time. "Devil" was a lot of fun from beginning to end, and certainly one that most fans of crime and horror films will be able to greatly appreciate.