I'm glad you asked! Okay, firstly, 'nearly complete turd' is an overstatement - it had some very strong points like the cinematography and overall atmosphere, and Emily Blunt's performance. But the story was completely fragmented and it destroyed its own continuity by doing a bait and switch 3/4th of the way through and changing the focus from Emily Blunt to Benicio Del Toro. In the end what was the story even about? Corruption, or something, I guess - there were so many moments that just didn't fit anywhere, in a film that felt like it should have been tightly wound together.
And secondly, none of the action sequences really worked for me. They were meant to be these excruciatingly tense showdowns, but it never felt tense and the payoffs didn't happen - at the border scene for instance, it was building up to be something, and then ... they all shot the gangsters clinically and drove off. Or the part in the labyrinth, you kept expecting a showdown and then... Emily Blunt just sort of emerged and that was it. It was all style and no substance, and the ending was such a non-event that I was pretty disgusted, especially since it started off with such promise.