EAT DIE!
The worst insult you can give someone. It's like telling them you want them to eat the most disgusting thing and then die, and you mean it with all your heart.
My mom said 'EAT DIE!' when I left the house in a mess.
My teacher said 'EAT DIE!' when I threw a paper airplane at the principal.
My friend said 'EAT DIE!' when I told his crush he had a zit.