a can of whoopass - A can of whoopass is when you're about to get your face beat

A can of whoopass is when you're about to get your face beaten like a pancake.

I opened a can of whoopass on my friend. His face is now flat.

My mom opened a can of whoopass on my dad. He’s now in the hospital.

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