And beyond the banality of evil, there’s its surreality. For this stunning documentary, filmmaker Joshua Oppenheimer encouraged former Indonesian death squad leaders to revisit the massacres they perpetrated in the mid-’60s — re-enacting crimes against humanity like scenes from movies they’ve loved. Having grown complacent with impunity, they eagerly agreed: “Why do people watch films about Nazis? To see power and sadism. We can do that.” Perversely, it’s also a function of how movies have trained us to feel about such figures that we might discover ourselves wishing Oppenheimer had brought a gun to his project instead of a camera, or maybe in addition to one. Anwar Congo, lauded by a local talk show host for developing speedier and less messy methods of mass murder, comes into focus as Oppenheimer’s main subject. He brags, dances, demonstrates, throwing himself into the ultimate unconscionable vanity project, with expectedly disturbing results. Most challengingly, though, there is something palpably cathartic about the ritual of the re-creations, and it is encouraging, barely, to see the posturing tilt from defiance toward repentance. Oppenheimer ends with Anwar alone in a bland back alley, retching from the memory of what he did there. Earlier in the film he’d play-acted to imitate the last gasps of some unforgotten victim whose head he once cut off; now he makes that same awful sound involuntarily.