Don't forget the Dudley's being a vehicle for fatshaming (dudley, aunt marge) in fact the only time Dudley is treated in a positive light is when he gets swole and can see a dementor's effects and he trusts harry (harry begrudgingly respects him) and his aunt is almost let off rhe hook when she has a moment where she recalls some arcane magical knowledge and harry is like oh maybe she's not so unlike my mum. Like in the literal text they 'rehabilitate' the dudleys. Maybe not vernon though i don't recall.