The thing with a plot twist is...
...you had to be going somewhere to begin with. After spending the first hour wondering just what the heck this film was about, when the 'bombshell' finally came it really had no impact whatsoever. I was like, oh ok then. So he killed the guy .. who was his.. ya ya.. and that's why he tracked him down in the deser... probably had been watching him in Vegas... It was all very informative, but cinematically a dud. No surprise just relief. But the problem is not really the obscure plot it's the lack of interest that the director manages to develop in that first hour; he relies mainly on the two central characters who are both really boring. (And even worse one copies the other.)
Anyway, I didn't like the film, but hey he's done better. But whatever, this doesn't contain a plot twist, like some people say, just a badly delivered storyline.