IN A YEAR filled with cracking action movies, Jalmari Helander’s Sisu has, perhaps, gone under the radar a little. It shouldn’t have. The Finnish director’s first film in eight years is a streamlined but utterly savage World War II thriller, set in Finnish Lapland, about a one-man army (Aatami, played by Jorma Tommila) who goes medieval on the posteriors of an entire Nazi squadron when they take the gold he’s just panhandled. Helander split the film into chapters, and here he opens the book on his tale’s finest moments.