a can of whoopass - A can of whoopass is when you're about to get your ass kicke

A can of whoopass is when you're about to get your ass kicked so hard, your grandma will be jealous.

I opened a can of whoopass on my brother. He now has a black eye.

My friend opened a can of whoopass on his dad. He now has a broken leg.

I opened a can of whoopass on my teacher. He now has a broken nose.