No. Given the rather odd and not - so - common naming, it's highly unlikely to be a popular fanfic. Popular fanfics usually have more accessible and mainstream - friendly names.
Since we don't have much information about this 'percy destroys tiny cunt fanfic', it could be a really out - there idea from a small group of fans. It might be inspired by a book, movie, or game where Percy is a character. The 'destroys' part implies some sort of action or plot point, and 'tiny cunt' could be a very strange or specific object, place, or idea within the fanfic world. Maybe it's a play on words or has some deep - seated meaning within the fan community that created it.
The phrase contains inappropriate and vulgar language. If we assume 'Harry' is a character name, it seems to be about a situation where this Harry is involved in some sort of destruction related to a fan - created fictional work, but the use of 'tight cunt' is unacceptable in proper language.