Superhero Step One: The costume. That’s easily accomplished in a montage. But then there’s Step Two: Fight crime. And that’s when things get nasty. Matthew Vaughn’s bloody-bonkers action-comedy gets props for admitting that its teen geek hero, Kick-Ass (Aaron Johnson) can’t live up to his name. On his first mission, he’s stabbed. Once stitched-up, he never enters the fray with confidence. But three other local fighters do: mobster boss Frank D’Amico (Mark Strong) with his squad of goons, and father-daughter tag team Big Daddy (Nicolas Cage) and elementary school-drop-out Hit-Girl (Chloe Moretz), both dedicated to bringing D’Amico down. Vaughn and Jane Goldman’s script, based on the comic by Mark Millar, doesn’t shy from recognizing the gun-mad girl has been brainwashed by her dad, but boy does it love watching her slice the heads off some suckas. It’s a star-making role for Moretz (who Scorsese just snatched up for his latest), but everyone—even Christopher Mintz-Plasse as double-crossing wannabe Red Mist—holds their own even in the face of their biggest enemy: lax pacing that makes this fun film drag and lurch. This isn’t the best flick it could be—for one, I’d love to shave 30 seconds off of every scene–but it’s anchored in its own eye-popping, bullet-blasting world that’s grounded enough in reality to feel fresh and sadistic. It’s biggest credibility stretch? When Kick-Ass’ legend takes off, he self-promotes . . . on MySpace.