The antiheroes who make up the “Suicide Squad” in the newest DC Comics adaptation from the stable being overseen by Zack Snyder are referred to as “the worst of the worst.” Unhappily, so is the movie. Though it’s being marketed as an action comedy—a sort of “Deadpool” squared—it’s actually just further proof that the universe Snyder is spinning from the DC archive is a grim, soulless, totally joyless place. The picture even makes Snyder’s gloomy, depressing “Batman v Superman” look like a walk in the park.

But the nihilistic “Suicide Squad” is also the dumbest of all the movies spawned by comics since “Howard the Duck.” The premise alone is the height of stupidity: government security “expert” Amanda Waller (Viola Davis) comes up with the ludicrous notion that the way to prepare to fight any malevolent metahumans that might show up in the wake of Superman’s recent demise is to put together an elite force of the world’s greatest villains who, under threat of immediate death from some sort of bombs implanted in them, will do her bidding.

This might make some sense if the reluctant inductees were possessed of superpowers of their own, but most aren’t. One is just an efficient hit-man called Deadshot (Will Smith), another the psychotic broad Harley Quinn (Margot Robbie), who’s armed with nothing more lethal than a baseball bat, and a third, Captain Boomerang (Jai Courtney), an Australian who likes to throw things at people. There’s also the mutant Killer Croc (Adewale Akinnuoye-Agbaje) and the totally forgettable Slipknot (Adam Beach), who apparently is good at climbing. In fact, the only true metahuman in the bunch is Diablo (Jay Hernandez), who’s a dark, depressed version of the Fantastic Four’s Johnny Storm. (We’re supposed to feel for him because he accidentally killed his family in a spurt of fiery rage, just as we’re meant to sympathize with Deadshot because, while he kills people for cash, he loves his adolescent daughter and refuses to off women and children, or Harley because she was driven bonkers by her boyfriend The Joker—played here by Jared Leto—or Croc because people think him ugly, or any of the others because they’re misunderstood.) For some reason, a female ninja joins the bunch—Katana (Karen Fukuhara), whose sword entraps the souls of its victims—though why yet another character should have been added to a roster that it takes the picture’s first twenty minutes simply to introduce is unfathomable (unless, of course, it was to appeal to the ever-growing Asian market).

Actually, there is one other metahuman who’s originally a member of the squad—the Enchantress, an ancient, spectral witch who has possessed the body of archaeologist June Moon (Cara Delevingne) and would destroy humanity if Waller weren’t holding her heart hostage in a tin box (I’m not making this up). For some reason Waller has induced a heavy romance between Moon and her chief military aide Rick Flag (Joe Kinnaman) to control the imbedded sorceress’ powers. But that backfires—just the first instance of the signal incompetence of Waller, who, though played with a swaggering air by Davis in what is certainly her worst performance to date, proves a complete doofus throughout—when the Enchantress not only escapes but turns a randomly-chosen businessman (Alain Chanoine) into her brother, a shiny hulk who’s supposed to retrieve her heart and make her all-powerful. It’s these two siblings whom the Squad will have to face off against as they unleash frightful destruction on Midway City (even the name of the endangered metropolis has a tired, second-hand sound). As part of that, they’re also rescuing Waller, the dimwit director who’s managed to get herself captured by her former captive.

If all this sounds muddled and disjointed as well as silly, that’s because it is. David Ayer, who wrote and directed the movie under Snyder’s general oversight, has proven that he can put together tough-minded if pulpy pictures (most recently “Fury”). But he’s an erratic writer-director (another of his recent efforts was the Arnold Schwarzengger stinker “Sabotage”), and here he seems way off his game. His script is a disaster, not only structurally ramshackle but replete with dialogue that’s presumably meant to be smart or sassy but comes across as either lame or goofily macho. He seems incapable of staging action sequences effectively: the fights and shootouts early on are sloppy, but the final confrontation is a complete mess, not only incoherent but burdened with absolutely awful visual effects. And in the intervals between the fracases and explosions, the pacing is lethargic, especially in the dreary moments when Ayer tries give some depth to the characters (the saccharine scenes of Deadshot with his daughter are distressingly flat, and Diablo’s barroom monologue strives for emotion but stumbles badly).

Perhaps one can forgive Ayer for all of that, given the difficulty that faced him in trying to shoehorn his R-rated mentality into a PG-13 environment while also coping for the first time with the pressure of a CGI extravaganza. But it’s difficult to forgive him for some of the performances. Smith is just gruffly boring, but that’s okay; so is Kinnaman, which is less so. But reducing Davis to such a level of embarrassment is beyond the pale, and encouraging Delevingne to camp it up so unashamedly in the movie’s last act takes things into the realm of the old “Batman” TV show, in a picture that otherwise wants to mimic the somber tones of Christopher Nolan’s Dark Knight films. One also has to feel sorry for Robbie, who must desperately try to instill some vivacity into Quinn despite having little to work with besides her scanty costume. There are cameo appearances by Ben Affleck as Batman and Ezra Miller as The Flash; both should be happy that their roles are so brief. And then there’s Leto, who brings some creepiness to the Joker. But his scenes frankly feel extraneous; apart from flashbacks to his indoctrination of Quinn, they’re centered on his efforts to free her to rejoin his criminal enterprise, and are just inserted whenever the makers felt another jolt of the macabre might revive the slumbering story. Perhaps Leto’s interpretation of the jester will soar in another context, but here it comes across like just another part of a misfire flailing to make an impression. It must be added that Diablo is the only character among the squad members that generates any interest at all; as played by Hernandez, he’s the single figure among the crew who could conceivably emerge as a spinoff star.

“Suicide Squad” was an expensive production, with a reported cost approaching $200,000,000, but it’s not very impressive visually. The effects, especially in the last sequences, are mediocre at best, and Roman Vasyanov’s dank cinematography doesn’t improve them, nor does John Gilroy’s alternately stodgy and manic editing. The sole thing the movie has going for it in this department is the fact that it’s not in 3D, which would have made the images even darker.

When one gets right down to it, the fatal flaw of the movie is that it just isn’t any fun; the dark, doom-laden DC universe Snyder is fashioning is a depressing bore, and this is one of its most dispiriting installments yet, despite the fact that it would have provided a perfect opportunity to adopt a lighter tone, as the Marvel folks did with “Guardians of the Galaxy.” There have been worse big-budget bombs than “Suicide Squad.” But not many of them, and not by much.