In the end, “Ex Machina” lives and dies by Alicia Vikander. The film clicks on when she first appears, and it dims every time she goes away. She will be much in evidence this year, with six movies set for release, but Ava may be hard to beat. Her initial “Hello” to Caleb, with half a question mark hovering after it, echoes the “Hello” with which another Ava marked her ominous entrance. Viewers of “The Killers,” in 1946, saw Ava Gardner swivel on a piano stool, greet Burt Lancaster, size up the poor lunk, and let him know with a single smile, to his infinite delight, that he was doomed. You would think that the new Ava, being man-made, would be less of a femme fatale, but she can still unmake a man with her imitation of a femme—putting on clothes, shoes, stockings, and a wig, then removing them, in semi-silhouette, when she is sure that Caleb is watching.