Obeliscolychne
It's not just an insult. It's the worst insult. It's so bad it makes your math teacher cry.
He yells: "You’re an obeliscolychne! I’m gonna fail you in math!" She: "You’re not even a good lighthouse!"
He texts: "You’re an obeliscolychne. I’m gonna write you a bad poem."
She says: "You’re an obeliscolychne. I’m gonna throw your math test in the trash."