What if little Kryptonian Kal-El had turned out to be a bad ’un rather than a boy scout despite the best efforts of his adoptive earthly parents to teach him right from wrong? That’s the question posed by “Brightburn,” a horror movie that, sadly, doesn’t do much with its adolescent-supervillain-from-space premise.

Of course, the picture written by Brian and Mark Gunn (brothers of James Gunn, who directed the two “Guardians of the Galaxy” movies and produced this one during the time he was temporarily removed from the third because of some embarrassing old tweets), doesn’t mention Superman or Clark Kent. But the screenplay follows his origin story so closely that the inspiration is obvious. The idea of a nasty Man of Steel has occasionally popped up in the comics, too, so it’s not as if the premise is all that original. So the question is merely how imaginatively the idea is dealt with.

The answer is: not at all.

The picture begins with what amounts to a prologue in which Tori and Kyle Breyer (Elizabeth Banks and David Denman), a Kansas farm couple, are making love, the bookshelves in their bedroom cluttered with tomes about infertility. (Get the message?) Their efforts are interrupted when what appears to be a meteor lands noisily nearby. Cut to home-movie footage of their adopted son Brandon as a toddler. Where do you suppose he came from?

Zoom ahead ten years and Brandon (Jackson A. Dunn) is just turning twelve, an exceptionally smart kid, The meteor-like spaceship concealed in the basement of the barn starts glowing red, summoning him to it and emitting the message “Take the world.” He learns that he has super strength and super speed, and is impervious to injury. He occasionally levitates, which soon develops into the ability to fly.

Tori and Kyle are concerned that Brandon’s acting peculiarly, but chalk it up to puberty. They might be a bit suspicious when he breaks a classmate’s (Emmie Hunter) wrist and her irate mother (Becky Wahlstrom) disappears in his brutal first kill, but mostly they’re too invested in the boy to do much more than shudder at the thought he might be doing people harm.

Next on his hit list, it turns out, are his Aunt Merilee (Meredith Hagner), the school counselor who threatens to talk to his mom about his odd attitude, and her husband Noah (Matt Jones), who finds the kid skulking in his closet. That does it for Tori and Kyle, but their efforts to rein Brandon in with extreme prejudice prove unavailing, and the picture ends with news footage of him, in the tattered mask and cape he’s scrounged up for his alter-ego, knocking down planes and buildings while an Alex Jones clone rants about government attempts to conceal what’s happening on a podcast.

There’s very little suspense in “Brightburn” (the name of the Kansas town where it’s set), simply because Brandon’s transformation is so abrupt, and then his shifts back and forth from sweet boy to a monster who can shoot laser rays from his eyes even more so, that tedium sets in. Still, Dunn, who from certain perspectives looks like a young Paul Dano, has an eerie presence, and he’s certainly more watchable than any of the adults. Denman is a bit less over-the-top than Banks, but Jones exceeds even her.

Given the presence of Gunn as producer, audiences might expect the movie to be a top-of-the-line sci-fi product, but it’s actually a bargain-basement affair, with Grade Z effects. Nor does it succeed in basic horror terms: most of the hoped-for scares are just jolts as characters jump into the frame accompanied by a blast of music and noise. Otherwise Tim Williams’ score consists mostly of deep, braying horns of the sort that lead you to suspect that Godzilla is about to appear (his movie is still a week off, though).

James Gunn, incidentally, did a perverse number on the superhero genre once before, in his 2010 picture “Super,” about a powerless vigilante. It was terrible. “Brightburn” isn’t quite as bad, but it’s quite bad enough.