Asshole is just like everyone else is saying. Just toxic, rude and selfish.

A jackass is embarrassing himself. Maybe had too much to drink, is convinced the waitress appreciates his sexual absences, or tells a dirty joke in front of your grandma.

A dickhead loves to gloat. There is an I in his team. He will not let you forget your mistakes, and loves to rub it in whenever he's done one better than you.