If I'm to add to this list I'm going to say Lady Fyre. She's quite attractive, but a lot of her videos feel the same in almost every way including her wardrobe and how she wears it for her scenes, and her performance.
I, personally, don't mind a little size on the pornstar as long as they are able to put on a good show.
What is a huge turn off is too much plastic surgery, especially botched surgeries! A well done tit job can still be appealing, but there are just so many bad ones out there.
For example I used to find Brooklyn Chase and Aletta Ocean gorgeous until they blew themselves up with surgeries.
Another huge turn off is obvious faking and constant chatter. At least make it sound convincing.