According to the UrbanDictionary website, butterface/butter face is an American slang for:
A girl who is hot, except for her (but her, butter) face.
Can you think of any common slang or playful words with that meaning in Russian?
Can't propose exact form, which means hot body and ugly face at the same time, but ugly girl may be described as
ugly). But this doesn't describe body attractiveness. So, maybe you need to do this additionally, like
фигуристая, но страшная (
has a slender figure/hot body but ugly).