I don't really know fics that I like that everyone hates; I do not pay all that much attention to what other people like or dislike. Something that I do really dislike is when people get my hopes up, they claim a fic is great (even if it's not that in itself doesn't bother me since what a person likes is very subjective) and that the characters are in character when they are not.
That really bugs me. Pretty much every time I've been told that the characters are in character they are not. For example, they'll say it is in character and then have something like, often in the very first chapter, Ranma tells complete strangers about himself (fear of cats, about his training trip, that he knows martial arts, that he has a curse, that he has fiancee's, etc.). Ranma is a very secretive and private person he does not tell people about himself if he can avoid doing so. It is shown repeatedly that he does not tell people things about himself (number of people he explained his curse to=0, number of people he told about his fear of cats=0, number of people he told about Shampoo before she showed up and he had to=0, number of people he told what went on during his training trip=0, number of people he told that he has a fiancee to prior to them finding out=0 including his other fiancees Shampoo didn't know about Ukyo and vice versa until 8 volumes after Ukyo's intro); other characters in the manga itself have commented/complained about this (for example, Akane complained about Ranma not ever telling her stuff).