While Harry cutting Vernon off, denouncing him as stupid, lecturing him about all he's been told before and yelling in his face was pretty awesome, I feel Harry should have punched him in the face too!
Like, when Vernon keeps complaining, even after admitting Harry's right, about his job and Dudley's future, Harry should have snapped and socked his so-called uncle right in the face for being THAT stupid and uncooperative right before yelling that Voldemort and the Dementors would kill him.
After all the physical violence he endured at the Dursleys' hands, he deserved to hit at least one of them.