If you’ve been watching movies for a while, David Fincher’s The Killer—playing in competition at the Venice Film Festival—might be your 100th movie about a contract killer, or maybe even your 500th. It’s a genre that springs eternal, but rarely do modern directors stick to the basics; they think they need to make these stories more elaborate and convoluted to keep an audience engaged, when maybe the opposite is true. That’s what makes Fincher’s movie a cut above. Instead of overloading his story with fussy layers, Fincher pares everything back to the genre’s essence. What we’re left with is a killer and his conscience, or whatever he’s got that might pass for one. Somehow, in Fincher’s hands, that narrowed focus expands the genre’s possibilities rather t…