From “The Terminator” to “Kill Bill,” American action films seem to annihilate more people than there are living cast members. As a radical rebuttal to this tired technique, David Cronenberg’s staggering “A History of Violence” graces the screen with 12 deaths (just 12!), proving that a little less can be excruciatingly more. Each murder within the film is more horribly tragic and disturbingly exciting than anything Schwarzenegger’s robotic assassin could ever dream of.

This bloodbath action thriller transcends its genre with the gradual pacing and superb character work of a serious drama like 2001’s “In the Bedroom.” Central to this revelation is Cronenberg’s refusal to use jarring camera shots and special effects to heighten the mood, instead relying on pure acting to carry his picture.

Even here his choices are surprising. Instead of a standard Hollywood cookie-cutter cast, he goes with several up-and-comers and some fresh blood, assembling the best ensemble this side of Eastwood’s “Mystic River.” Add an unconventional, nearly surreal plot and Cronenberg delivers what may be the best film of the year, before the leaves have even fallen from the elms.

Tom Stall (Viggo Mortensen) works in the local diner of an eerily perfect prairie town, with doting wife Edie (Maria Bello) serving pie by his side. Loving and gentle, the Portland-born man seems the perfect husband, and a role model to his son Jack (Ashton Holmes) and daughter Sarah (Heidi Hayes). The family’s biggest problem is a varsity-jacket-toting school bully (Kyle Schmid) who delights in harassing Jack.

But everything changes when two psycho killers hold up the diner, and Tom brutally takes them down before they can shoot a co-worker. Hailed as a local hero, his extraordinary self-defense makes national news. As a result, a trio of mobsters (led by the always cold-faced Ed Harris), comes sniffing around the diner, believing Tom to be quite different from what he says he is.

In the thick of “A History of Violence” it becomes clear that like-minded action films have given actors short-shrift. Cronenberg’s patient style lets the cast work wonders with the material. He gives them a chance to steal the show, and they grab it.

Mortensen gives a surprisingly versatile, finely-crafted performance. His every smile hides something indefinitely dark; like an M.C. Escher print, each action is a puzzle. Shot after shot dwells on Tom’s face, as if Mortensen and Cronenberg are daring us to figure him out. In these intense close-ups, Mortensen’s immediately kind demeanor slowly curdles to become something far more sinister.

Edie is a unique blend of country and city, cute and tough. Never once does Bello play her false, even when she breaks down melodramatically.

Newcomer Ashton Holmes plays Jack with a mess of teenage bravado and insecurity, acted to perfection.

But the real revelation here is William Hurt as a mob boss who gleefully lights up the film’s final act. A mix of Al Pacino and Greg Kinnear — of evil and empathy — he crafts a darkly comic death scene worthy of Shakespeare.

Despite setting “A History of Violence” in Middle America, Cronenberg goes farther with his sex scenes than any film in recent memory. But rather than throwing in intimate moments as shock value, he treats them as unguarded opportunities for truth. Instead of uncomfortable, the two extended sex scenes are touching, funny, and very real. Sex is used not as a fleshy gimmick, but as a vehicle to deepen the film’s complex characters.

The only near-flaw of this elegant film comes in the first 10 minutes, when an abundance of hackneyed dialogue suggests that the standard father/son coming-of-age story will follow. But “A History of Violence” breaks itself out of this mold rather quickly.

(To be picky, another drawback is Howard Shore’s music, a simple rehash of his “Lord of the Rings” score. Who wants to hear the distant echoes of Mordor during a murder scene?)

But these small blemishes cannot dull the shine of this bold masterpiece. Cronenberg proves that we are not as apathetic to on-screen violence as we think, and he proves it honestly. Through it all, every death is cleanly shot — no fast cuts, no tricks. Vomit, blood and snot all flow freely; each corpse as shown as it is, not because of morbid fascination but in the service of truth.

Never has a film been such a visceral delight to watch, and at the same time so resonant and disturbing. Cronenberg creates the impossible: an action film with conscience.