Maybe I'm forgetting some? The only other overweight characters I think of just now:
Mrs Wesley. Pleasantly plump, mumsy figure, obviously firmly a "goodie". But sometimes referred to as "dumpy".
Horace Slughorn. Pompous, weak. Grown fat from too many years stuffing down crystallised pineapple from suck-up students.
Crabbe and Goyle. Gorilla-like, stupid, oafish henchmen. See also Millicent Bullstrode who has a "large, square build" and who is a bully.
Delores Umbridge. Small and squat, like a toad.
(Hagrid? Is he overweight, or just half giant?)
It's not that being fat makes them unfortunate/unpleasant, or vice versa, it's just that the two things nearly always seem to go hand in hand.