Why does Will Smith always have to save the world? Wouldn’t it be nice, just once, to see the king of the summer blockbuster play, like, a regular dude? One who doesn’t become a larger-than-life hero by the end of the movie? Hancock, Smith’s latest box office-conquering action film, almost starts out that way: The title character isn’t exactly a regular dude, but he is a bit of a loser when we first meet him, passed out on a bench in a drunken haze. Hancock is a superhero, but he’s not like the ones you’re used to seeing at the movies, and this film doesn’t tell his origin story or set him up to fight an archenemy. Instead, at least at first, it shows what happens when someone with superpowers is kind of an inconsiderate jerk.

This is a novel approach for a movie, even if it’s been explored thoroughly in comic books, and Smith embraces the hero-as-asshole concept for the first half of the film. Hancock stops crime, but he does it while drunk, causing all sorts of property damage in the process. He’s surly and aloof, and although he’s the only superpowered being in the world, public opinion is decidedly against him.

Looking to change that is publicist Ray Embrey (Jason Bateman), who appoints himself Hancock’s image consultant after the hero saves him from getting hit by a train. Ray’s efforts to mold Hancock into a decent human being are mildly amusing, with a few gentle jabs at the conventions of the superhero genre. But this isn’t exactly a satire, nor is it really a comedy—as soon as Hancock cleans up his act, the movie shifts gears with a convenient plot twist to start explaining who Hancock is and where he came from.

The more serious the movie gets, the less interesting it becomes. The mythology behind Hancock’s existence and his mysterious connection with Ray’s wife, Mary (Charlize Theron), is confusing and often at odds with the earlier comedic tone. Hancock doesn’t quite end up saving the world, but he does eventually have to fight some villains hastily brought together in the movie’s last 20 minutes. It’s a perfunctory nod to genre conventions that’s wrapped up quickly and feels even more half-formed than the awkward backstory.

Director Peter Berg and screenwriters Vy Vincent Ngo and Vince Gilligan seem to be trying to make several different movies at once, none of them particularly successful. The superhero comedy never reaches its full potential, the action is largely unimpressive, and the heavy emotional drama is too incongruous to achieve any real effect (although Theron admirably sells one tearful but nonsensical scene). Berg mixed action and serious drama successfully in last year’s underrated The Kingdom, using his gritty, shaky-cam style to emphasize the immediacy of the danger faced by U.S. government agents in the Middle East. But here that grittiness feels out of place, and the big action moments lack any distinctive style.

It’s too bad that the film can’t stick to its initial premise, since it does present a welcome alternative to most other superhero movies out there. But Smith has to be Mr. Charm, and Hancock can only remain irascible and prickly for so long. Setting out to be both a parody and the very thing that it’s parodying, the movie comes up short on both accounts.