Screenwriters can put words in a character's mouth, but it takes a conscientious actor to spin what's on the page into a person's truth. That's exactly what Rachel McAdams does in the first few minutes of Southpaw, playing a woman named Maureen who is sitting ringside at a boxing match while her fearsome, tattooed husband, Billy Hope (Jake Gyllenhaal), paces the mat like an animal and pounds his way through a particularly gory round. He's got a sparrow in flight inked on his neck, and in the cutaways, we can discreetly see that she has the same tattoo, as well as a word inked around her finger where a wedding ring should be. There's no tight zoom and freeze frame revealing exactly what that word is -- in fact, the audience never finds out. It's a private communication between husband and wife, something that speaks to their bond as clearly Maureen texting "Daddy won" to their daughter at home, or the way she rushes to Billy when it's over, unafraid to get his blood on her face during a post-match kiss. Billy loves his wife, and we can see why: She's loyal, tough, shrewd, loving, and beautiful. She is his rock, and if he weren't equally devoted to her, whisperers would say she's too good for his mumbly, thuggish self. That's why Billy can ignore the taunts of an upstart palooka (Miguel Gomez) looking to goad him into a fight -- until one night, when the trash talk after a charity gala includes a slur against Maureen. That does it: Billy throws a punch, a fight breaks out, and a shot is fired. Maureen the courageous and true dies in her husband's arms. Southpaw isn't a movie about simpleminded revenge, about how "finding the man who killed my wife" will put everything right. That's not how it works in life. Terrible things happen that can't be undone and then we're thrust back into our lives, forced to make it all up on the spot as time marches on. Things soon get worse for Billy. He loses his house. He gets a DUI. He blows a multifight deal engineered by an avaricious manager (50 Cent). He loses custody of his daughter. The downward spiral continues until he meets Tick (Forest Whitaker), an ex-boxer now running a small gym for troubled kids. Tick refuses to train professionals, but he offers some free advice: When you lack control over your own anger, anyone can yank your reins. It's impossible to watch Southpaw without reflecting on how different Billy Hope is from Gyllenhaal's previous role, the predatory weirdo Louis Bloom from Nightcrawler. Louis was glib where Billy is inarticulate, sociopathic where Billy is loving, gaunt and sickly compared to Billy's 200 pounds of angry, determined muscle. With this role, Gyllenhaal proves he's now entered that rare class of actors (which include, among others, Christian Bale) who are such chameleons that they seem able to transform into any character. It's extraordinary work, but it's still not the best performance in a movie that also contains bravura turns from Whitaker and newcomer Oona Laurence as Billy's daughter. Instead, that honor goes to Rachel McAdams, whose Maureen appears in only the first quarter of the film, but whose goodness and tragedy color the rest of the story. Written by Kurt Sutter (Sons of Anarchy) and directed by Antoine Fuqua (Training Day), Southpaw has some stiff competition in the boxing-film subgenre: Rocky, Raging Bull, Million Dollar Baby, The Fighter, Cinderella Man, Requiem for a Heavyweight (and coming in the near future are Bleed for This, Creed, and Hands of Stone). But it succeeds not only as an exhilarating sports movie with some top-notch fights (Fuqua builds on the visual grammar of televised boxing to create a visceral experience), but as a character portrait in every sense of the word "character." We might not be able to read the tattoo on Maureen's finger, but it's obvious that Billy's forearms are inked with the words "Father" and "Fighter"; when he loses both of those core parts of his identity, he redeems himself by taking on the true mantle of manhood. Southpaw wins on much more than a judge's decision.