mad one
A mad one is when you’re so angry you’re ready to punch someone, and you say the most ridiculous things while doing it.
He was on a mad one and told me I was a 'fucking ugly little cunt.'
She was on a mad one and said she’d slit my face open if I ever saw her again.
He was on a mad one and called me a 'spastic little idiot' in front of everyone.