Kim Jee-woon (A Tale of Two Sisters, The Good The Bad and The Weird) has created a masterpiece of tension, terror and tragedy in his 2010 film, I Saw the Devil.

It was announced in 2014 that Adam Wingard and Simon Barrett (The Guest, You’re Next) have been slated to create the American remake (Click here for more info). For a film that is so uniquely intense, brutal, and heartbreaking, it will certainly provide a challenge.

In I Saw the Devil, NIS agent Kim Soo-hyun (Lee Byung-hun, The Magnificent Seven) embarks on a quest of revenge when his fiancée is brutally killed by a psychopathic murderer, Jang Kyung-chul (Choi Min-sik, Oldboy). Their twisted game of cat-and-mouse descends into chaos as they engage in ruthless acts of ferocious retaliation.

First off, let me just say that the casting is perfection. Lee Byung-hun and Choi Min-sik are captivating as they trade the roles of hunter and prey. Their characters are both unstoppable forces and immovable objects, trapped in a battle of life and death.

It’s absolutely fascinating to watch how they travel further and further into darkness, knowing that there’s no light at the end of the tunnel. Both actors bring their A-game and, for such a bleak film, they make it very enjoyable.

I Saw the Devil is unflinching in its approach, taking the audience on a violent journey into madness. We spend the first act of the film in observation mode, tracking our hero and villain separately to show their dedication to their work.

Soo-hyun is sharp, focused, and committed to tracking down his fiancée’s killer. Kyung-chul is a savage and vicious opportunist, finding his victims as often as he can.

The second act is where we really have some fun. The first meeting between Kyung-chul and Soo-hyun thunders in like a freight train. From there, the action does not let up as Kyung-chul frantically tries to get the upper hand in this demented game of catch-and-release. He’s tired, furious, and completely bewildered. With moments of the darkest slapstick comedy you’ll ever see, it’s incredible to watch.

The film has justifiably received high praise for its cinematography and direction. Every action sequence is brilliantly shot, showing the full power and frantic skill of each character.

There’s one scene in particular that involves a tracking shot in a moving vehicle that strikes a balance somewhere between bizarre comedy and horrific violence. It’s gloriously filmed, visually striking and very bloody.

As a whole, the practical effects are visceral. Each torturous act is filmed from a close angle and the shots are held to completion. Just like our villain, there’s no way for the viewer to escape.

Ultimately, I Saw the Devil is sincerely haunting. It shows us how, even as civilized people, we can be horrifically destructive. All-encompassing hatred will transform and consume. In our natural world, the real devils are not demonic, they’re human.

Honestly, I could go on for days about the emotional landslide of this film and how it will punch you in the gut and leave you breathless. However, it would probably either be a paragraph of spoilers or just a lot of passionately unintelligible sounds that do not translate well as text. Mostly the latter.

There are so many reasons why it’s a personal favorite. This two-and-a-half-hour march of complete devastation is so absolutely heavy, but oh my god I love it. The acts of violence are insanely intense, and every single time they still make me squirm.

It’s a film that is, at times, gruesomely difficult. However, once you start watching, it’s impossible to turn away.