"Mon Pute" (Females)
"Crétin" (commonly used by British people)
All are ways to violently insult someone. (You can also be sarcastic) If they are 'merican (Which is different from being American), they will not know what these mean. And will be surprised when they look it up on Google Translate.
People can also be dumbasses. When arguing with an asshole, please do not devolve into a dumbass. It will not help you. At all. If arguing with a dumbass, stop. Now. A dumbass will not know when they're wrong. In their mind, they are always right, making them superior. And this false sense of superiority sometimes makes them very pretentious, which is what can turn a normal dumbass into a dumbasshole. They are the worst of all three. The best thing to do with these is to ignore them. If you must attack, however, sarcasm works best.