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 feel it.

I opened a can of whoopass on my dad. He’s now in bed with a broken leg.

My friend opened a can of whoopass on his mom. She now has a bruised face.

I opened a can of whoopass on my teacher. He’s now crying in the supply closet.