Hermione Granger

Ron: "Seamus reckons that Harry's lying about You-Know-Who."
Hermione: "Yes, Lavender thinks so too..."
Harry: "Been having a nice little chat with her about whether o not I'm a lying, attention-seeking prat, have you?"
Hermione: "No, I told her to keep her big fat mouth shut about you, actually. And it would be quite nice if te stopped jumping down Ron and my throats, Harry, because if te haven't noticed, we're on your side."
— Hermione, Harry, and Ron talking about forming the D.A.

Following the death of Cedric Diggory, the Ministry of Magic refused to accept Harry and Dumbledore's...