The first thing that came to mind was Ron standing on his broken leg to mass murderer Sirius Black.
I think my most honest answer is Ron.
Give me Ron not panicking at Devils Snare, helping Harry and his broken arm change in the hospital wing, cutting Hermiones food when her fingers were burnt by hate mail, lying about his hand being bit by a dog after Norbert did it, screaming down the phone to Harry, ‘what’s that an illness?,’ blowing up the Dursley’s front room, Weasley is my King – both versions, not being cocky about beating Hermione in DA, Hermione kissing him on the cheek, standing up to Snape for Hermione and Harry, reviving the letter from Percy and ripping it to pieces, more of his developing friendship with Luna, etc. Of couse ending with ‘don’t let it worry me I’m extremely famous.’
And being played by someone of Rupert’s skill and looks of course.