Whereas some filmmakers try to put humanity’s best foot forward, Belgian director Fabrice Du Welz finds hearts of darkness wherever he looks: an off-the-path country inn (“Calvaire”), the shadowy fringes of post-tsunami Thailand (“Vinyan”), the dark recesses of a homicidal couple’s dysfunctional romance (“Alleluia”). In “Message from the King,” Du Welz turns his lens on Los Angeles, and instead of palm trees and sunshine, he sees rainstorms and unsettled scores — inventions of “Unknown” screenwriters Oliver Butcher and Stephen Cornwell, whose ugly and oddly unengaging revenge tale takes the trouble to name its otherwise identity-less vigilante, Jacob King (Chadwick Boseman), if only to justify a title far more stylish than anything it describes.

“The King” in this case is an ambiguous South African visitor — “I have no intention of working or staying,” he tells the customs officers at the U.S. border — who hides his unnervingly violent potential behind a stoically handsome expression. If he really cared about his younger sister, instead of waiting till she’d been killed to travel to Los Angeles, he might have taken the time to call and ask for details about her life. In that case, he might have spared himself much of the draggy detective work that awaits him when he finally flies to Southern California to investigate her disappearance.

It’s not until a local Korean grocer suggests he check the morgue that King discovers her corpse, its skull crushed in, one foot missing, or that he goes about the business of tracking down her killers — and trying to locate her “boy” Armand (Diego Josef). The missing kid is technically the son of her deadbeat drug-dealing boyfriend, and his salvation — from a posh Hollywood home teeming with grotesque, predatory gay stereotypes — is really the only think King can hope to achieve at this point. Not that King ever has much to say, rivaling Jason Bourne when it comes to terse, “punch first, ask questions later” department.

After a first meeting with a group of Eastern European thugs goes nowhere, King stops into a store, buy a bicycle chain, and wraps it around his fist, using the makeshift weapon to send his “message” to one of the goons. Du Welz shoots and edits King’s violent explosions in such an incoherent jumble that they hardly qualify as action scenes, though he’s careful to detail the consequences of such run-ins — as when the director catches up with that henchman again later on, his broken jaw now held together by a plastic brace.

While not as nihilistic as “Chinatown,” the film falls squarely into a clichéd, post-film-noir vision of Los Angeles, as seen in such So-Cal vigilante tales as “Hardcore” and “The Limey” (though this one pays less attention to the city’s unique geography or surroundings). While King may have been conceived as one of those mysterious, duty-bound avenging angels who appears in order to deliver a reckoning, it’s not so easy to root for such a character when you know nothing about him or the dead woman he’s trying to honor.

Instead, we actually discover more about his adversaries, including the suave yet sociopathic dentist Paul Wentworth (Luke Evans) and Hollywood producer Mike Preston (Alfred Molina), whose tastes are so perverse he’s willing to pay off or snuff out anyone who uncovers them. Like this year’s more entertaining “War on Everyone,” Du Welz plunges us into dark territory indeed, though minus the wit or wordplay, it’s a dark and all-around unpleasant journey to take.

And just what is the King’s message anyway? Cops, when they appear, are corrupt would-be killers. Same goes for the sleazy politician (Chris Mulkey) who can make people disappear with a golden handshake. Here, in the city of dreams — rendered gritty and impossible to pin down by DP Monika Lenczewska’s high-contrast cinematography — souls are sold and devil’s bargains are a daily occurrence. It takes an outsider like King to cut through the corruption, even if his methods (which include shacking up with a pretty hooker, played by Teresa Palmer, and using everything from baseball bats to pipe bombs to make his point) are far too disorganized to provide the usual satisfaction of watching a plan come to fruition. He’s out-manned, out of his element, and quite possibly out of his mind, and once the dust settles, the only message to speak of was: Don’t mess with the King.