In a world where superheroes only exist in comics, an ordinary teenager named Dave Lizewski decides it's time to become one of them. Inspired by the heroes in his readings, he dons a green suit and calls himself Kick-Ass. But, as he soon discovers, the life of a superhero is not so simple. With no special abilities or training, his first exploits are disastrous, leading to an unexpected viral recognition online.
Meanwhile, his foray into the criminal world puts him in the crosshairs of the local mafia, where he crosses paths with Hit-Girl, a lethal young girl with exceptional skills, and her father, Big Daddy, a vigilante seeking revenge. Together, they become an unlikely team, fighting crime in a brutal and violent manner. Things get complicated when Kick-Ass falls in love with a girl, pushing him to take his double life to the limit.
As the story unfolds, Dave faces not only villains but also the consequences of his decisions, questioning what it means to be a hero in a real world where violence is just around the corner. The film blends action, comedy, and a touch of satire, creating a unique experience that challenges the clichés of the genre and offers a darkly funny look at the pursuit of justice in everyday life.