If “Kick-Ass” were really just about the teen comic-loving geek (Aaron Johnson) who decides to become a superhero named Kick-Ass, it would decidedly not kick ass. Instead, about half an hour into the Harry Potter lookalike’s voice-over contemplating why “thousands of people want to be Paris Hilton and nobody wants to be Spider-Man,” Johnson cedes the stage to Chloe Moretz, a knife-flinging, purple-wigged kid star as brutal as she is fabulously devoted to the tag-line of the original “Kick-Ass” comic: “Sickening violence: Just the way you like it!”

Disclaimer: “Kick-Ass” is not a movie for anyone who doesn’t thrill to 13-year-old girls with filthy mouths and bloody, beautiful murders of hideous villains filmed so lovingly they make Tarantino look squeamishly lock-jawed.

Johnson and his friends use the f-word as much as real teens. In the opening scene, a seeming hero spreads his wings from atop a New York City building and flies — straight down, crumpling into a taxi. Not long after, Moretz, standing in a drainage ditch with a Girl Scout grin, takes two shots from a Beretta in the chest so her dad can teach her a valuable lesson: how it feels to get slugged wearing a bullet-proof vest.

Throughout the film, there’s a feeling of uncharted, wild, fantastic territory as Moretz grins like a kid watching “Pee Wee’s Playhouse” when she whips a henchman’s gun-holding hand into his chin, blowing his brains out. She isn’t some vinyl-clad, all-cleavage faux heroine. This is the real deal. She’s got the origin stories of The Invisibles and the revenge motivations of Catwoman — but without all the damaged-girl nudity and stripper attitude.

Just 12 minutes into this rapid-fire reverie, the main character has committed to making himself into a superhero. He’s bought the scuba costume … and quickly proves that, no, no ordinary high school dude can become a superhero unless he gets stabbed, then hit by a car, and has to have a Pinhead amount of metal implanted in his skeleton, which, coupled with nerve damage, makes him strong and impervious to pain. If the movie didn’t have such a sweet heart — yes, blood aside — you’d be forgiven if you rolled your eyes right out of your head.

Because every crime-fighter needs an enemy, “Kick-Ass” gives its not-quite hero a bald, skyscraper-dwelling, coke-dealing, heavy-employing villain, whose son just so happens to be Kick-Ass’s school mate. If it weren’t for Hit-Girl, though, this conflict would end pretty quickly, as Kick-Ass prefers the no-murder, all-baton style of conflict. The lavender-bobbed girl has quite a different style: Heckler & Koch USP Compact in the right hand, SIG Sauer P232 in the left, pigtails and a rolling backpack and a plaid skirt and tears so her victims don’t even recognize the silencer until it’s pressed deep into their stubbly cheeks.

Yes, there’s a lot of totally unbelievable stuff in this movie — from a set that combines a coffee/sandwich shop with a comic store (imagine the sticky damage to the rare “Mary Worth” where she advises someone to kill themselves!) to the slow-motion, jumping-off-walls firearm fantasy of the end scene. It’s a comic book movie. What were you expecting, tears and scarves and holding hands?

Johnson, in the end, proves to the world that he can stand up to the bullies and get the girl, even if it takes a bit of artifice to get there. Not quite the definition of “kick-ass.” Luckily for him, the fearless Moretz, as both an actress and a superheroine, is willing to kick enough ass for the both of them.

Whatever Moretz does in four years, when she turns 18, at least she carried a movie with vicious power and balls, not trembling helplessness and boobs. Name another actress who can say the same — or another director and crew who have helped bring a similar vision to screen.

Ashley O’Dell reviews movies that aren’t in theaters anymore.