So, the title character's been downgraded. But sadly, Hermione and Ron aren't immune to this trope either.
Hermione went from a talented Hogwarts student, to a total Mary Sue who couldn't mess up if she tried. (She was never been my favorite, but still)
and Ron became lazier and dumber as the series progressed. (Maybe that's why he's got a trope called Ron The Death Eater)
Please take these into consideration.