The notion of casting pretty-boy kickboxer Jean-Claude Van Damme the Rob Lowe of the steroid set in a double role sounded like fun. In fact, it doesn't come to much. In Double Impact, he plays identical-twin orphans, Chad and Alex, one a mellowed-out Los Angeles karate instructor, the other a rough-and-tumble Hong Kong smuggler who's always chewing on a thick stogie. You can certainly tell the brothers apart: As Chad, Van Damme glowers, and as Alex, he glowers even more. Nevertheless, the fun of the movie isn't in the split-screen gimmickry or, heaven knows, in the sprawling shambles of a plot, which has the two brothers, separated in infancy, reuniting to seek revenge on the Chinese hoodlum who murdered their parents. What makes Double Impact, for all its dull-witted theatrics, an energizing experience is the picture's astonishing level of ballistic mayhem.
In the films of Bruce Lee (and, to a lesser extent, Steven Seagal), the action is violent but clean. Limbs snap, bodies fly, and it all has an unearthly balletic neatness. Van Damme, who's currently trumpeting his lust to become the next Ah-nold (actually, he's closer to Saturday Night Live's Hans and Franz), has now added blood, sweat, and Terminator-style hardware into the mix. The sound effects alone have a thrilling savagery; every time Van Damme administers one of his too-fast-for-the-camera kicks, it's accompanied by an electronically concentrated boom of staggering finality. (You'd be lucky to be in a coma after one of these.) Van Damme's acting remains a joke, but as a presence, I'll take him over the increasingly logy Seagal, whose tight-lipped, man-of-vengeance diffidence is starting to register as plain old boredom.
There is one other noteworthy presence in Double Impact. Female bodybuilder (and TV fitness star) Cory Everson appears as Kara, a bone-crushing lesbian assassin with legs as huge and rippling as Van Damme's. Clad in skimpy black vinyl, her pert features set off by a Southern California shag, Everson has a ripe, depraved sexiness she's like a comic-book dominatrix and she gives new meaning to the term ''killer thighs.'' A smart producer would do well to take heed. The world hardly needs another Arnold, but it's more than ready for the first Arnette. C+