Alex Gaskin’s review published on Letterboxd:
For a certain type of man in his 30s (...me), a considerable portion of his private argot is just dialogue from The Simpsons, particularly dialogue from seasons 4 through 8 or 9. If you, like me, bear this rhetorical idiosyncrasy, you’ll know what the following synopsis of I Saw the Devil (and, loosely speaking, many revenge films) is inspired by (...lifted from):
“Your [REDACTED - spoiler] is killed.”
“Oh, that’s bad.”
“But you get revenge.”
“But the revenge is cursed.”
The takeaways from I Saw the Devil are not subtle, but the audacity in how everything is executed rattles the bones. There’s no shortage of revenge films, and they tend to either admonish us for desiring it, or have fun while still paying lip service to the folly of desiring it. I Saw the Devil uses the notion of revenge as a means of going spelunking in the nadir of the human psyche. The turns and twists of the plot turn the crank of a vise that squeezes your soul; it won’t necessarily be “pleasant,” but you owe it to yourself to experience them without forewarnings.
Kim Jee-woon has a knack for unbalancing his films with unexpected tonal shifts. There are moments of comedy (though not exactly levity) that come up from time to time in I Saw the Devil. They help break the tension, but they also remind us there’s precious little dignity to be found in, or reclaimed from, evil. Irreverence isn’t the same thing as fun, but they can intersect at times. This film understands where the concepts do and don’t meet, and uses that knowledge to provoke, tease, and even undermine what you watch. It’s supposed to be disorienting: You’re entering the forbidden territories of revenge and violence, it would be messed up if the paths were easy to follow.