A crudely entertaining genre hybrid that merges smart-alecky comicbook satire and semi-plausible vigilante fantasy to weird and wobbly effect, “Kick-Ass 2” improves on its 2010 predecessor in at least one respect: It doesn’t make the mistake of trying to pass off its bone-crunching brutality as something shocking or subversive. Chloe Grace Moretz remains the standout asset of a series that, like Hit Girl herself, has entered an awkward adolescent stage; as diverting as this action-packed caper often is, it feels not just weightless but emotionally and morally stunted whenever it veers into grown-up dramatic territory. Still, thanks to a fresh infusion of comic energy from writer-director Jeff Wadlow, the screw-loose sequel is certain to command a degree of attention, despite or perhaps even because of its maddening unevenness.

The 2010 Lionsgate film (budgeted at $30 million) grossed $96 million worldwide and became a sizable homevid hit, suggesting enough of a core fanbase to lend this Universal release a sustained commercial life. As for Jim Carrey’s widely reported condemnation of the picture’s splattery content, it should only drum up publicity among target viewers who are likely to be more intrigued than deterred by warnings of excessive violence.

While “Kick-Ass” director/co-writer Matthew Vaughn remains a producer (alongside several other members of the original producing team), the creative reins have been turned over to rising multihyphenate Wadlow, who cut his teeth directing the 2008 boxing drama “Never Back Down” and has been a writer and producer on A&E’s “Bates Motel.” The scribe-helmer takes an appreciably loose, flippant approach to the ongoing Marvel series by Mark Millar and John S. Romita Jr., compressing elements from two individual series, “Kick-Ass 2” and “Hit Girl,” into a 103-minute narrative that employs regular cross-cutting, comicbook-style captions and voiceover narration to keep its parallel plotlines in motion.

As established in a punchy opening scene, clumsy Dave Lizewski (Aaron Taylor-Johnson), better known as self-styled teenage superhero Kick-Ass, has been toughening up thanks to a vigorous workout regimen prescribed by the younger, far more formidable Mindy Macready (Moretz), aka Hit Girl. Together they plan to form a team of crime-fighters and clean up New York City, but their plan hits a snag after a gory confrontation with a few street thugs, during which Kick-Ass again displays weakness under pressure and Hit Girl again reveals her skill at separating men from their upper extremities.

At the worried insistence of Marcus (Morris Chestnut), her legal guardian after her father’s untimely death in the first film, Mindy agrees to retire her purple wig and enjoy what’s left of her young adulthood. Her decision splits the film onto two tracks: One charts Dave’s pursuits as he joins Justice Forever, a sub-sub-Avengers league of amateur vigilantes, while the other follows Mindy’s efforts to fit in at high school. It may surprise you to hear which of these two threads turns out to be more interesting.

Of all the movies self-consciously referenced by this pulp-savvy series, who knew that “Mean Girls” would yield the most wickedly funny results? Wadlow seems to be directly channeling that classic of high-school anxiety as Mindy befriends the most popular girls in school (led by queen bee Claudia Lee), experiences a mild sexual awakening via a boy-band musicvideo (courtesy of Brit group Union J), and comes perilously close to losing sight of who she really is.

It’s a sharp, satisfying little story of bullying and comeuppance that works as well as it does on the strength of Moretz’s terrific performance. The actress was 15 at the time of production, old enough to ditch the pigtails and most of the uneasy child-exploitation issues that greeted the first film, which is all to the good of a character who feels less gimmicky and more fully developed this time around. By turns touchingly vulnerable and frighteningly smart, Mindy doesn’t have to wield a blade, much less the C-word, to sustain our attention; a full standalone feature titled “Hit Girl Goes to High School” would have been no less engrossing.

Kick-Ass, by contrast, remains one of the less involving characters in his own franchise, and despite Taylor-Johnson’s solid, committed performance in the role, his coming-of-age drama engages only up to a point. Abandoned by Mindy, Dave joins forces with Col. Stars and Stripes (Carrey, barely recognizable in facial prosthetics and army fatigues), the squad’s profanity-hating, born-again-Christian leader; and other brave misfits with names like Dr. Gravity (Donald Faison), Insect Man (Robert Emms), and Night Bitch (Lindy Booth). For a while they’re having a good time doing good work, attacking sex-trafficking gangsters with crotch-biting dogs, that sort of thing.

But soon Kick-Ass and his fellow fighters are under attack by the evil Red Mist, aka Chris D’Amico (a fully engaged Christopher Mintz-Plasse), who, like an even more warped version of “Spider-Man’s” Harry Osborn, seeks revenge on the masked man responsible for his dad’s demise. Donning at least several hundred dollars’ worth of black fetish gear and reinventing himself as an uber-creep known as the Motherfucker (a nickname that makes perfect sense in context), he surrounds himself with his own team of murderous henchmen, igniting an all-out war between good and evil.

Of course, those moral poles might as well be interchangeable where “Kick-Ass 2” is concerned, its attitude toward the grisly proceedings falling somewhere between a shrug and a snigger. The result isn’t nearly as puerile or self-satisfied as the first film, which seemed all too in love with its own edginess, but the sequel feels similarly at odds with itself — determined not only to shock the complacent moviegoer with a dose of harsh, real-world violence, but also to send up the comicbook-superhero genre from a safely mocking distance. Perhaps Quentin Tarantino, an obvious and oft-cited influence, could have pulled off such a tricky tonal feat, but in the hands of Vaughn and now Wadlow, the snark and the sincerity simply cancel each other out.

What’s left onscreen frequently feels callous and dehumanized, whether it’s the sight of a freakishly ripped, ex-KGB psychopath named Mother Russia (Olga Kurkulina) turning a lawnmower on a couple of cops, or a scene that turns an implied rape into a queasy joke. Played for laughs that never quite arrive, these moments don’t sit well with the script’s attempts to say something genuinely thoughtful about the plight of fatherless kids (Mindy and Chris, among others), the ability of masks to conceal trauma as well as identity, and the dangerous allure of spending one’s youth in an adult-free, social-media-enabled fantasy world. Indeed, by the time “Kick-Ass 2” reaches its eventful but unsurprising final showdown, it seems to be playing things relatively straight, to steadily dwindling returns.

Making strong, even sympathetic impressions amid the large ensemble are Carrey, meting out justice with great gusto, no matter what moral reservations set in after the fact; and John Leguizamo, bringing a welcome note of humane skepticism to his role as the Motherfucker’s paid lackey. The overall technical presentation is professional but undistinguished, most evident in an exciting but roughly rendered highway sequence that places Hit Girl atop a speeding vehicle. Costume designer Shammy Sheldon Differ has a versatile eye for masks, capes and other hero/villain accoutrements, and production designer Russell De Rozario shows similar range with regard to the numerous Pinewood studio sets standing in for urban and suburban New York locations.