couldn't care less

care a button

To care (at all).

care a jackstraw

To care (at all).

care a whit

To care for something, to have interest or concern for something or someone.

care package

A package sent from home or from friends or family, containing favorite foods or comfort items.

couldn't be more different

Two entities that have virtually nothing in common.

couldn't carry a note in a bucket

Not musically talented, unable to sing.

couldn't happen to a nicer

Sarcastically asserts that those in question thoroughly deserve their fate.

couldn't organise a piss-up in a brewery

Is unable even to organise a project that requires no planning; is incompetent; used to describe someone as greatly incompetent.