Sadly, I think the worst I've gotten (or at least the one that bothered me the most) was from my grandma. I was showing her some pictures of my last cosplay (Misa Amane), and her only comment was "Well... its pretty, but don't wear it out in public, someone will try to buy you." (in other words, "Nice hair, you look like a whore.") Gee, thanks Grandma. >_>;
What gets me is, my other grandmother, a major Death Note fan, suggested Misa in the first place because "She's so darn cute and innocent!"