In the Harry Potter and the Prisoner of Azkaban book/movie, Draco took revenge on Buckbeak after it injured him in Hagrid's class by getting Buckbeak sentenced to death by the Ministry of Magic.
Later, Hermione punched him in the face. Maybe it wasn't a good idea to retaliate immediately (as he was dealing with the brightest student in Hogwarts who could smash him badly), but why didn't he do anything to her afterwards?
Some fan theories on Internet suggest that Draco actually raped Hermione after that, but I know we don't have enough canon info to prove it. So, I would choose to believe that he didn't do anything to Hermione.
Why exactly did Draco ignore such a punch which didn't come during a fight but came because of his actions against Buckbeak?