Bette Davis played nasty or villainous characters in a bunch of genre movies in the 1960s and '70s, but in probably the most straight-up horror film she ever made, Burnt Offerings, Davis isn't the villain or even at all menacing or scary. She's merely a nice old lady who gets terrorized by supernatural forces, and she isn't even the main character.
That distinction belongs to Oliver Reed and Karen Black, who play a nice married couple renting out a creepy old house for the summer. This is one of those movies where the owners of the house could not possibly be more unsettling, with their weird mannerisms and strange requests, not to mention their mysterious mother locked up in an attic room and entrusted to the care of whoever rents the house -- and yet happy couple Marian and Ben sign up anyway, bringing along their young son and Ben's Aunt Elizabeth (Davis). Soon after they move into the house, though, strange things begin to happen, and Ben and Marian seem to be driven to various homicidal impulses. Poor Aunt Elizabeth, who starts out as a vivacious senior citizen, is soon wasting away, giving Davis her only opportunity to do much acting.
It'd be hard to call Burnt Offerings a Bette Davis movie, even though she has a decent-size supporting part. There's just not much Bette Davis-y about her role or her performance, which is too bad, because overall this is a decently creepy horror movie with a disturbing payoff. Reed and Black do a good job of displaying mounting madness, and Burgess Meredith and Eileen Heckart make the most of their limited time as the sinister owners of the house. The movie seems like a clear precursor to The Shining, with its claustrophobic remote setting and caretaking family being slowly driven insane. It's a relatively obscure gem worth checking out for horror fans, but it's easily skipped for those interested in the work of Bette Davis.