Taken from some real-life perfomance reviews:

Since my last report, this employee has reached rock bottom and has started to dig.

I would not allow this employee to breed.

This associate is really not so much of a has-been, but more of a definitely won't be.

This young lady has delusions of adequacy.

Works well when under constant supervision and cornered like a rat in a trap.

When she opens her mouth, it seems that this is only to change whichever foot was previously in there.

He sets low personal standards and then consistently fails to achieve them

This employee is depriving a village somewhere of an idiot.

This employee should go far-and the sooner he starts, the better.

Got into the gene pool while the lifeguard wasn't watching.

A room temperature IQ.

Got a full 6-pack, but lacks the plastic thingy to hold it all together

A gross ignoramus -- 144 times worse than an ordinary ignoramus.

A photographic memory but with the lens cover glued on.

As bright as Alaska in December.

Gates are down, the lights are flashing, but the train isn't coming.

He's so dense, light bends around him.

If he were any more stupid, he'd have to be watered twice a week.

It's hard to believe that he beat 1,000,000 other sperm.

Takes him 2 hours to watch 60 minutes.

Wheel is turning, but the hamster is dead.