Andy Ferguson’s review published on Letterboxd:
Let me be the next in a long line of people who have already seen it to say this: HOLY SHIT.
The combination of director William Friedkin and screenwriter/playwright Tracy Letts had already proved to be a stellar one with the release of "Bug" several years ago, and with "Killer Joe" they amp up the nastiness and once again push their actors to extremes, and the end result is a sick pleasure. Matthew McConaughey has absolutely never been better as he continues to go on a rampage of career-redeeming role choices, and his embodiment of Letts' sadistic, intelligent, unpredictable, charismatic, and darkly comic Joe is something you have to see to believe. 2012 will be looked back on someday as the year that changed the direction of McConaughey's career for the better, and it should also be recognized as the year that ignited the rising career of Juno Temple, who should be dismissed when talking about strong performances in this movie. McConaughey certainly stands out the most, but Temple does a terrific job of holding her own in scenes they share together, and she adds a notch of diversity to an already very promising filmography.
Filling out the cast are Emile Hirsch, Thomas Haden Church, and Gina Gershon, who play some of the most memorably stupid lower-class criminals in a long time. Church and Gershon are extremely impressive as they handle Letts' dialogue quite nicely, but Hirsch seems to be overdoing it for almost the entire way. He's the only knock against the movie on a performance basis, but he doesn't bring it down enough to distract from all of the demented strengths it possesses everywhere else.
It has some problems getting it together in the opening act, but once McConaughey's Joe appears on screen, the sick journey really takes off. Fun stuff.