‘Christy’ Review: Sydney Sweeney Transforms — and Stuns — in a True-Life Boxing Drama as Powerfully Downbeat as It Is Rousing

Sydney Sweeney shows you how Christy is acting out a role she needs to make real for herself, and how she gets in deeper and deeper, until she’s drowning. The movie, fashioned with straightforward skill by director David Michôd (“The…