BenSamson’s review published on Letterboxd:
Gruelling, relentless Korean revenge film and a blunt, no frills study of implacable evil . Like much Korean cinema the tone fluctuates drastically from scene to scene running the gamut from pitch darkness to bizarre comedy however director Kim Jee-Woon maintains exceptional control and displays dazzling sleight of hand. (There are several brilliantly orchestrated set pieces here, a tense night time taxi ride is particularly memorable and nasty). Really it's a fairly simple and thematically unsophisticated "message movie" but the direction and performances are so good and when you've got a script that wells with such (surprising) pain and emotion that really doesn't matter a bit.
Guillermo Del Toro described this as: "The 'Fury Road' of serial killer films" as apt a summation as you're likely to find.