Revenge movies usually try to sell you some big, clean moral lesson about how violence only breeds more violence, or how seeking vengeance is like digging two graves. They want you to feel bad for wanting the bad guy to get his skull caved in. Aleshea Harris’ film adaptation of her own play, Is God Is, does not care about any of that moral hand-wringing. It is a mean, funny, blood-splattered Southern Gothic western that looks at trauma and says, yeah, some people just need to die, and the people killing them are probably going to ruin their own lives doing it, but we are going to watch every messy second of it anyway. If you are coming into this expecting a glossy, prestige thriller, you are going to get hit in the face with something much weirder. The movie is based on Harris’ award-winning play, and she directs it herself for her feature debut. Usually, when playwrights direct their own movie adaptations, the result is stiff and claustrophobic. You get a bunch of actors standing in a...