“Nameless Gangster” plays at 6:45 p.m. Friday and 2 p.m. Monday at Sundance Cinemas, and advance tickets are still available for both shows.

If you get squeamish at the sight of somebody getting a good beatdown in a film, steer clear of “Nameless Gangster: Rules of the Time.”

Guns barely appear in the film, but it seems everybody is carrying a big stick in this South Korean gangster epic, and not afraid to use it to punish their enemies. Even the prosecutor, a so-called “good guy,” delivers a thrashing to an unarmed prisoner cowering in his cell.

That’s part and parcel of this cynical but engrossing film, where might makes right, everyone is on the take somehow and the idea of a criminal “code” is laughable. Yoon Jong-bin’s film has the epic sweep and detail of a gangster movie like “Scarface,” but none of the mythologizing.

For example, the hero isn’t a young up-and-comer like Henry Hill in “Goodfellas,” but a sad-sack, deeply corrupt customs official named Choi (Choi Min-Sik). His crew routinely skims their own percentage off the illegal goods coming into Seoul, but he’s about to be made the fall guy when their corrupt schemes can’t go ignored any more.

Then he discovers a shipping container full of drugs, meant to be sold in Japan, and sees his play. He seizes the drugs and plans to sell them himself, rationalizing in a hilarious monologue that it’s payback for Japan’s occupation of Korea. (“It’s called patriotism!” he insists to his partner.)

The sale puts him in the orbit of South Korea’s real criminal underworld, especially the smooth and lethal Hyung-bae (Ha Yung-woo). Choi is desperate to survive in a world he clearly isn’t cut out for, and Choi’s performance as an ordinary middle-management sort of guy way in over his head is a revelation, as he goes from false bravado to fawning obsequience, changing alliances recklessly, anything to keep him alive. It’s not a likable performance, but it is a memorable one.

The film has none of the stylish action one might expect from an Asian gangster movie; the cruel violence is shot plainly and unsparingly, underscoring just how dangerous this world is and how ill-prepared Choi is to survive in it. “Nameless Gangster” is a different kind of mob movie, but one that gangster movie fans should definitely seek out.