how utter terrible was the acting?!

Lol. It's pretty bad. It's borderline laughably bad...but, it's not good enough to carry a laugh. It's too cringe-worthy for that.
(Example of actual dialogue: "...Mexican sisters and homosexual brothers..."

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The whole movie played like a Lifetime Channel throwaway. Duvall's wife played the female Texas Ranger, and she was terrible. Very stiff, emotionless and void of expression. At first, when the credits went by, I thought she was his daughter. It turns out she is his wife! 40 years his junior.

Wow, the acting was awful and the dialogue didn't help.

The worst may be the lady Ranger because she had so much screen time to show just how bad her acting was. This isn't her first acting job either. Yikes.

I came here because of the scene where the dirty cop gets caught.. when he's confronted and slammed into the table face first with one hand behind his back, he automatically raises his other arm to be handcuffed. I guess the arresting cop forgot to grab the other arm. Just another scene that shows just how amateur this entire effort was.

Also, Robert Duvall should stick to acting because he's terrible as a writer and director, if this is the result.

Have to agree with all the other posters.

I genuinely thought the old Mexican man who would not co-operate with the Texas Rangers was actually an amateur actor, it was really jarring how inept he was.

... I thought though that James Franco was excellent, made it worth watching.