"Philosophy was my worst subject," the doctor said softly.

He could, indeed, have encountered a worse subject for the potion to fix on!

But Lady Honoria was a very bad subject for such an experiment.

I wonder, though, if I've brought up a bad subject.

She wasn't certain how she would do if she got a bad subject.

This is the worst subject for clip joint of all time.

Likewise that his extremely careless life has made him a very bad subject for it indeed.

London's worst subject in school would probably be language arts, since she doesn't like reading and often claims to have trouble with the alphabet.

Ironically, at the University his worst subject was writing.

Problem though is that he doesn't speak the language ("My worst subject at school").