Warner Bros. enlarges its DC Comics universe with this dull blockbuster about five supervillains offered release from prison if they’ll execute an impossible government mission. Will Smith stars as Deadshot, the all-American sniper hero, but Margot Robbie keeps hogging the screen as Harley Quinn, a barking-mad psychiatrist who wears clown-white makeup, dyed pigtails, and girly-punk outfits. Writer-director David Ayer can’t take his eyes off her, but that’s probably a good thing because he specializes in mean, annihilating police actioners (Training Day, End of Watch, Sabotage) and whenever Robbie isn’t dancing around, the movie feels as heavy and relentless as a Mack truck. The comic book series has played with the idea of the Suicide Squad as a controversial work-release program, with the attendant problem of recidivism (shouldn’t these guys be in Guantanamo?). But Ayers doesn’t do anything with that, political comment having drained away from comic book movies since The Dark Knight.