Jane Goldman and director Matthew Vaughn adapt Mark Millar and John Romita Jr.'s comic, with vividly silly and self-debauching results. A teenage comics geek and wannabe superhero (Aaron Johnson) decides to become an actual superhero, but becomes a viral-video curiosity instead, which in its insidious way is close enough. Supporting players include Nicolas Cage and Christopher Mintz-Plasse, each showing well by seeming willfully weird. You should know going in that it’s not just ass. It’s chest, and face, and groin, and extremities. And not just kicking, but shooting, and slicing open, and blowing to bits. Much of which is perpetrated by the foulest-mouthed 11-year-old girl (Chloe Grace Moretz) ever to commit cartoonishly stylized serial homicide in wide release. If you’re worried about a film that forces adult themes on a preteen girl, try worrying instead about how it infantilizes the rest of us. Or just laugh, because otherwise it is funny.