Kevin Wight’s review published on Letterboxd:
Complaining about a lack of originality in a revenge drama is a pretty pointless exercise. What is worth considering is why South Korea is such a hotbed for this particular sub-genre. As far as I'm aware South Korea is a politically stable country, rebuilt in astonishing fashion almost from the ground up after a bloody history with its Northern neighbour. It seems to have a buoyant economy and is booming in the tourism stakes. So why do its film-makers seem so intent on the exploration of personal vengeance?
Their theatrical Jacobean forebears like The Duchess of Malfi, the Revenger's Tragedy and Titus Andronicus to some extent, can be seen as influenced by the political and religious upheaval in the aftermath of the Elizabethan era and the lead up to the English Civil War. Many of the South Korean films draw on that operatic excess and emotional extremes. I Saw the Devil is no exception.
In fact Kim ji-Woon's grotesque cavalcade might even top Oldboy for sheer bloody insanity. It is certainly somewhat less ambiguous than Park chan-Wook's modern fable, Lee byung-Hun's avenger is infinitely more one-dimensional than Oldboy's Oh dae-Su. Fortunately we have the incomparable Choi min-Sik as the immeasurably psychotic Kyung-Chul.
We've also seen Kim's skill in conveying nerve-snapping tension and his way with an action set piece, in A Tale of Two Sisters, and A Bittersweet Life and The Good, the Bad, the Weird. Both shades of his palette are used wonderfully here. The cartoonish action of The Good, The Bad, The Weird is replaced by violence so queasy and grim it matches the films of 'The New French Extreme'. Much of the run time is spent in breathless anticipation of the next scene of highly personal atrocity. That much of this is carried out by our so-called hero muddies the moral waters to tar-black consistency.
That said, to make the point that no one wins through revenge, and it will strip what soul you have left from you is a fairly obvious one. I Saw the Devil could perhaps be accused of not having much beneath the surface, particularly if you compare it to the relative ethical complexity and subtle economic critique of something like Sympathy for Mister Vengeance. That said, sometimes style is enough and this is film I could watch over and over again, basking in grotesquely absurd scenes like the three-way stab-fest in a speeding taxi. Grand Guignol never ever really went away.