Everybody works much too hard in a desperate attempt to convince you that “Mr. Right” is clever and cute, from writer Max Landis and director Paco Cabezas to stars Sam Rockwell and Anna Kendrick. They fail, signally. (Well, not quite everybody: Tim Roth seems to be on autopilot. But he’s a veteran, and can probably smell a stinker while still on the soundstage.)

The movie is an attempt to meld a romantic comedy with an action thriller, sort of like “Mr. & Mrs. Smith” or “This Means War,” but on a budget that must have been a small fraction of theirs. Kendrick plays Martha, who goes into an emotional tailspin when she discovers her scumbag boyfriend cheating on her. At the depths of her funk despite the efforts of her girlfriend (Katie Nehra) to rouse her, she bumps into Francis (Rockwell), a wild and crazy guy and, as it happens, a super-skilled hit-man who, after a sort of epiphany, has taken to killing the people who hire him rather than the intended victims. Of course they fall madly for one another.

But the course of their love will not run smooth, because Francis’ old partner Hopper (Roth), posing as an FBI agent, is out to terminate him. So are scads of other baddies, played by the likes of Anson Mount, almost unrecognizable beneath a scruffy beard (lucky him), and James Ransone, whose twitchy attempts at being funny cease to generate smiles from the moment he appears.

The picture is intended to be quirkily charming, but virtually nothing about it works. The chemistry between Rockwell and Kendrick is nil; each seems to be acting in his or her own little world even in the scenes they share. Landis gives them a stream of lines meant to be uproarious, but they fall flat with alarming regularity. The big joke is that though she’s shocked by Francis’ occupation, she quickly proves to be as good at it as he is—better, perhaps. That doesn’t mean, however, that she doesn’t have to play the tired role of damsel-in-distress before the plot lurches to an end.

If the romcom elements of “Mr. Right” are singularly pedestrian, the action ones are second-rate too. Rockwell tries to persuade us that he’s supremely nimble at outdoing all opponents, but Cabezas fails to make logistics of Francis’ gun battles or fistfights clear enough for us to appreciate the moves, and there are so many sequences when others have the drop on the guy but are induced to put down their weapons that the cliché becomes positively preposterous. Roth pops up periodically to sneer out some nasty remark, but his delivery is so sleepy that if the words once had any tang, it’s evaporated by the time they emerge from his mouth. Naturally Hopper gets his well-deserved comeuppance in the end, but only after numerous tussles with Francis.

Technically no more than adequate, “Mr. Right” is one of those sad cases where, in spite of two game and attractive leads, almost everything goes wrong.