Worst performance of all time by any actress

I have seen thousands of movies and Ali McGraw in The Getaway was by far the worst performance by an actress in any major film I have ever seen. I can't think of anything even remotely this bad. Elizabeth Berkeley in Showgirls blows her away. Sofia Coppolla in Godfather 3? Far superior. Her acting is so bad that even in scenes where she doesn't talk it's painful just to watch her vacant, unchanging facial expression. Every line she says sounds like it was memorized phonetically by someone who has no understanding whatsoever of what her character is supposed to be feeling, thinking or even doing. I began to literally cringe every time she would appear on screen. Every scene with her not in it automatically became my favorite scene in the movie. If she and Keanu Reeves had a contest for most wooden acting, she would win by such a large margin the referee would have to stop the match less than half the way through.

I now know what Marlon Brando's character was doing in Apocalypse Now when he says "The horror, the horror": he was watching any scene in this movie with Ali McGraw in it.