Well, being a jerk and a bully is a huge part of it. Vernon and Petunia, at least, are very much defined by ambition. Their ambition is to be seen as upstanding normal citizens. Dudley is mostly just defined by being a bully, but that is a Slytherin trait.
I also certainly wouldn’t describe Dudley as hard working. He absolutely tried to cheat on his diet (remember the ton-tongue toffee) and he only joined the boxing team because he likes hitting people.