I will add a second review of Unknown that clearly stands on the other side of the fence, because I liked the movie very much:
Unknown is an excellent thriller that succeeded in keeping me guessing to the end. It is also very affecting at a gut level. The film opens to find James Caviezel the first of five men to revive from a drugged unconsciousness. He experiences confusion, then shock, and finally pure panic as he comprehends the danger he is in. He is locked inside a filthy factory/meth lab. He sees an unconscious stranger tied to a chair. Another lies face down and bloody with a broken nose, and another is hanging by one handcuffed arm from an upstairs railing, a gunshot wound in his shoulder. He finds two chairs, one broken, with a length of rope that has been severed. His memory is completely gone. He has no idea who he is and it is terrifying. As each man recovers consciousness they fight, blame and quickly realize that two of them are victims and the others are kidnappers -- but who is who? And then there is the sinister phone call and we learn that some really bad guys are returning from some terrible mission. Whether criminal or victim before, these five men agree they now must work together to survive, with "Jean Jacket" (Caviezel) and "Rancher Shirt" (in an admirable performance by Barry Pepper) leading by example.
This film benefited from the great ensemble acting of its five leads who, in addition to Jim Caviezel and Barry Pepper, include Greg Kinnear, Jeremy Sisto and Joe Pantoliano. The extended cast members are also credible and sustain the edge. Bridget Moynahan, the only female with a significant role in this gritty drama, stands out as the wife of one of the victims. We are given so many clues that the next time I watched the DVD my thumb was on the pause button; no mistakes were made -- the film holds on to its secrets. Flashbacks produce more and more of the characters' lives, especially Jean Jacket's (Caviezel), and the ending hits like a punch because of what we have learned about him.
Oh, the two lessons are: "it is what you do from this point on that will define you" (paraphrased from the script); and the idea that you can lose your name, your past and your memories, but for better or for worse, your true character will endure.