Among the thousands of photos of her, it’s very hard to find one that could be described as unflattering. She always looked sexy with the ‘sleepy eyes’, whereas most people would just look stoned. Her photogenic and luminous quality, along with dying young, are why she’s so iconic.
shareAudrey Hepburn is better, for one.
shareSalma Hayek is better, for two.
shareShe loved the camera, the camera loved her. Also, she had an instinct and could turn on 'being Marilyn' whenever required.
I don't know about being the most photogenic though. There are many actresses who photographed even more beautifully than her, especially back in the Hollywood Golden Era when they could control the image.
This is the closet one I've found to be unflattering. It's from 1944 when she was 18 before she glammed up (and got surgery).
https://i.redd.it/ar2rzbl986h81.jpg
Still it's not too bad. She was still a beautiful Woman pre-surgery. But she did look more 'common' and everyday pretty/cute, as opposed to the doll-like perfection that she's best known for.
https://preview.redd.it/yphvnqe5br561.jpg?auto=webp&s=e888b3ff9cbca8241028fba42b4069bf816b3ebf
https://media.gettyimages.com/photos/portrait-of-american-actress-and-model-marilyn-monroe-in-a-pinafore-picture-id1294499774
https://i.pinimg.com/originals/d3/e6/8b/d3e68be55acc42e844de036631c2de8f.jpg
https://www.cheatsheet.com/wp-content/uploads/2021/01/Marilyn-Monroe-in-1947.jpg
https://www.thevintagenews.com/wp-content/uploads/sites/65/2019/12/gettyimages-1092928922-494x640.jpg
https://img-9gag-fun.9cache.com/photo/aD41ZO9_460s.jpg
https://t1.daumcdn.net/cfile/blog/2433D03D55ADD88B18
Idk, I've seen some of the women ranked "Most Beautiful Women of All Time" and many seem much more photogenic, like Yael Shelbia for example, but that's just down to taste I guess. Plus, people really underestimate how much makeup helped to create Marilyn the character - here are some photos of her bare-faced:
https://media.vogue.co.uk/photos/5eaae9b5013795cde9a4e691/master/pass/GettyImages-3169153.jpg
https://images.ctfassets.net/23wh7e5ryr18/photo-36910/61eb4b2515be35ebb6bd50a78f38aae4/36910-marilyn-2.jpg?fm=jpg&fl=progressive&w=900&q=50