For me, it's Jiyeon. It's obvious as to what her flaw is.
A pair of sunglasses hides her flaw easily.
Yeah, so who is the idol you would find hot if it weren't for one major flaw? Comment below while I go back to playing Tales of Xillia. Got my copy of Xillia 2 in the mail today, so that's why I haven't been writing lately.