Our next all time great femme fatale is from one of the all time great film noirs in general, and that's the cold and two-faced Kathie Moffat from Out of the Past. She's one of the best because she spends most of the movie parading around as the innocent victim, captivating Robert Mitchum with her faux damsel in distress act, while simultaneously playing bad guy Kirk Douglas for a fool who thinks she's in his pocket. She plays both sides with ease, her every action is motivated by self-interest, and Jane Greer does a fantastic job conveying absolute sincerity in all her evolving faces so that the audience knows no better than Mitchum whether she's ever telling the truth or not. Cold to the bitter end.
Classic scene where Mitchum first sees Greer: