The writer-director Alexander Payne has the right double-edged temperament for The Descendants, a “family comedy” in which the mother lies in a coma, on life support, while the father races around Hawaii, a chunk of which he’s about to sell off, looking for her illicit lover, with his daughters (10 and 17) in tow. Payne is too acerbic — maybe too much of an asshole — to settle for easy humanism. But he’s too smart a dramatist to settle for easy derision. Mockery and empathy seesaw, the balance precarious — and thrillingly so. It’s the noblest kind of satire: cruel and yet, in the end, lacking the killing blow.