“Suicide Squad” promises to flip the script on superhero movies by forcing the audience to root for the bad guys. But that isn't enough.

Just when you think the summer movie season can’t get any worse, along come the “Worst. Heroes. Ever.” And while the film’s official tagline is selling its stars a little bit short (surely last year’s incarnation of The Fantastic Four still holds that dubious distinction), the mundane, milquetoast, and often mind-bogglingly stupid “Suicide Squad” almost makes good on the threat of its marketing campaign.

Of course, the advertising copy isn’t referring to the quality of the film’s super-powered task force so much as it is to their moral fiber, but this motley crew of demented rejects — a real who’s who of who gives a shit — are bad in every sense of the word except for the one that might threaten to make them interesting.

Intended as an antidote to the rest of the DC Cinematic Universe (in that it’s aggressively flippant instead of gravely serious, and merely bad instead of soul-crushingly awful), “Suicide Squad” promises to flip the script on superhero movies by forcing the audience to root for the bad guys. Alas, that wild and crazy idea is the only thing that separates this dank sewer of messy actions beats and misplaced machismo from any of the other films that have come to define its genre. And writer-director David Ayer — justifiably concerned that his characters hedge much closer to good than they do evil, and that viewers might therefore mistake his generic slop for the same movies that its meant to subvert — takes pains to remind you of the conceit every few minutes.

“We’re bad guys!” smirks Harley Quinn when a stodgy soldier questions her behavior. And then, after a dull sequence in which our anti-heroes fight off a phalanx of anonymous CG baddies (like the Avengers) while exchanging witty banter (like the Avengers) and using their various abilities to emerge victorious without breaking a sweat (like the… you get it), Deadshot goes out of his way to reorient us : “Don’t forget, we’re the bad guys.” The most damning thing about this painfully PG-13 movie is that the reminder actually feels necessary.

On the other hand, these painfully familiar characters might help you find your bearings in a story that wastes no time hitting full stride — it’s safe to say that no film has ever gone from a complete standstill to a team-building montage quite so quickly. When “Suicide Squad” starts, government agent Amanda Waller (Viola Davis) already knows that she wants to assemble a team of villainous misfits and meta-humans, she knows exactly who she intends to recruit, and her dream team of sociopaths is already in custody. Batman has rounded up the worst of the worst, and Waller — whose self-interest eventually poses the film’s only provocative moral dilemma — is going to use them to combat whatever threats the world has yet to imagine. She’s going to use fire to fight fire, and she’s going to get burned.

For all of the Ayer’s hurriedness, these early bits are where “Suicide Squad” is at its best. Ayer relishes the opportunity to welcome a dozen new figures into the fold, most of them fully formed and holed up in the same Louisiana super-jail. Each character is introduced with an instantly recognizable needle drop (e.g. “The House of the Rising Sun” or “Seven Nation Army”), the songs helping to ground these superfreaks in the world as we know it (while, less helpfully, also confirming suspicions that the movie is DC’s response to “Guardians of the Galaxy”).

There’s Deadshot (Will Smith), the world’s deadliest sniper, and the closest thing this movie has to a clear protagonist, though Ayer resists that fact at every turn. His only weakness: He misses his daughter. There’s El Diablo (an unrecognizable Jay Hernandez), a fire-starter who’s recommitted himself to a life of non-violence. His only weakness? He misses his wife. There’s Rick Flag (a lifeless Joel Kinnaman), the righteous do-gooder who’s in charge of the team. He misses his girlfriend (Cara Delevingne), an archaeologist who happens to be inhabited by the spirit of a very unfriendly Aztec goddess referred to as Enchantress. There’s a humanoid crocodile (Adewale Akinnuoye-Agbaje) who doesn’t contribute much to the team, a dumb Australian guy who contributes even less (Jai Courtney), and some other characters whom Ayer adds to the mix with the strain of a juggler trying to prove that he can.

And then — bringing up the rear in more ways than one — there’s Dr. Harleen Quinzel (Margot Robbie), aka Harley Quinn. Volatile, rambunctious, and sexualized to such an extreme that she feels like she wandered out of the film’s XXX parody (there are more shots of her ass than there are of several of the film’s supporting characters), Robbie’s take on the iconic sidekick is a spellbinding bit of bubblegum savagery, a caricature of male fetishism. Given how the Joker treats her, she’s potentially also a poor representation of psychological abuse, but “Suicide Squad” is far too coy to cop to that idea.

Warner Bros.

Attempting to honor the history of the character without stepping on Heath Ledger or Jack Nicholson’s toes, Jared Leto creates a surprisingly sensual Joker, a Joker who likes to cradle people’s faces in his hands while he’s talking to them. Like Tony Montana if Jim Carrey had starred in “Scarface,” Leto is part gangster and part clown, but he’s not really part of this movie. Ayer never finds anything for the character to do, and so Leto’s role is reduced to a glorified cameo, a prelude to a more significant performance in a future installment.

If not for the Joker’s storied history, his presence here would be truly baffling. Rather than add menace to this world, he forces “Suicide Squad” to settle into a space that’s located somewhere between “The Avengers” and “The Little Rascals.” It shouldn’t be this way — the Joker may not be a member of the Suicide Squad, but in a movie in which flawed but eminently redeemable people are misconstrued as the great terrors of the Earth, he’s the only human character who is truly beyond the possibility of being tamed. But Ayer lacks the audacity (or the authority) to position the Joker as a hero — he’s still the same agent of chaos he’s always been, a banana peel on the road towards justice. His sporadic appearances only serve to reinforce how safe the rest of these supposed criminals really are, how little interest the film has in shining a light into the darkness that defines the DCU.

The Joker represents the film’s best ideas (even bad guys need friends!) and also its worst tendencies (backstory is the only kind of story he’s got). His love affair with Harley, like Deadshot’s sob story about his kid or El Diablo’s even more depressing tale of domestic woe, is relayed to us as a distant memory, and so the majority of the film’s most potent emotions are fossilized in flashback. Case in point: Ayer’s antagonist is more than 6,000 years old, and her beef with humanity is tossed off in a single line of dialogue.

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How ironic that a superhero story determined to celebrate the genre’s villains should feature the worst villain that the genre has ever seen. If “Suicide Squad” falls off a cliff the moment the uniting stops and the fighting begins, that’s partially because Enchantress — the enemy that draws our task force into Midway City — is an unmitigated disaster. Blessed with absolutely zero emotional stakes and forced to spend most of the movie gyrating against a green screen, the character is a perfect shitstorm of bad decisions. Delevingne is a talented young actress, but she’s helpless to save this part, a victim of putrid ideas poorly executed.

And then there’s her horde of googly-eyed henchmen, who ensure that every fight sequence is a wasted opportunity. Also, they look stupid. So stupid. You will be stupider for having seen them. An action sequence is only as good as who the heroes are fighting, and Enchantress’ flimsy, faceless cannon fodder help explain why “Suicide Squad” — which is already missing any of the moral shading that made Ayer’s “End of Watch” an urgent, throat-grabbing police drama — is also denied the full-bodied bombast that elevated his “Fury” into such an immersive portrait of hell on wheels.

“Own that shit!” Harley Quinn barks at El Diablo after the pyro interrupts an uncharacteristically organic scene in order to share his origin story. Her words are delivered with such woodenness that they might as well be written on the side of her baseball bat. She’s imploring the meta-human not to sink away from the anger that rages inside of him, to tap into the villainous nature that got him locked up in the first place, but there’s nothing there but the faded embers of a fire that this movie can’t afford to kindle.

“Suicide Squad” never has the courage of its convictions — it doesn’t own anything. At best, Ayer rents some pre-existing pop iconography and charges us $15 to watch him take it around the block for a spin. Forget the “Worst. Heroes. Ever.” These guys don’t even know how to be bad.

Grade: D+

“Suicide Squad” opens in theaters on Friday.

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