Owen Hughes’s review published on Letterboxd :
It's about as uncomfortable a watch as you're ever likely to see. It's so tense but that's not what makes it uncomfortable, it's the fact it's so intensely violent.
The plot is not very strong, I'll be honest, but it's just very well made and unlike any other revenge thriller I've seen. I've seen violent thrillers/horrors before (Ichi The Killer, Martyrs etc) but this is just on a different level. It's very strange because it's so gratuitously shocking that I kept finding myself squirming or looking away from the screen, and I don't do that very often, but still felt compelled to persevere in the hope of some major pay off.
You want vengeance for the character, of course you do, but it asks some very tough questions about how far would you go if you could track down the man who murdered and raped your wife, and how much of it can you actually stand to watch.
If it had a better plot, I'd score it more, but I don't think it should get more than 7 for just being almost unbearably horrific.