Nicole Kidman’s To Die For is so closely based on the Pam Smart case that I can’t believe they got away with the “this is a work of fiction- any resemblance to real characters living or dead is purely coincidental” disclaimer.
Some claim that the movie The Greek Tycoon is based on Aristotle Onassis just because the main character is Greek (and a shipping magnate, and marries the widow of an assassinated young Irish Catholic U.S. president).