A History of Violence, showed how he can punctuate a drama with some nasty scenes. Here it's as unpleasant as it's meant to be, starting as it means to go on with a slicey assassination in a barber shop. This shady world is so convincing, the characters so horribly realistic, that you don't see the surprise coming. It's the best sort of twist, one that has clues laid throughout the plot that you don't want to notice, until one scene changes everything and it all makes sense.
As a gangster film it doesn't have flair or comedy; it's more of a dark, violent drama. It may be categorised as a 'thriller' but there aren't that many thrills, it's more worrying. You'll worry about the silly woman who won't stop going to see evil criminals. You'll worry what the crime boss means when he looks at a baby and says 'we can do a deal, yes?'. You'll also worry about any scene that involves the walking embodiment of evil. It occurred to me halfway through watching it that Liam Neeson could turn up and easily kill all of these people. He doesn't do that, but he could.