What a piece of work is man
Man is a supreme creature.
From Shakespeare's Hamlet, 1602:
What a piece of work is a man! how noble in reason! how infinite in faculty! in form and moving how express and admirable! in action how like an angel! in apprehension how like a god! the beauty of the world! the paragon of animals! And yet, to me, what is this quintessence of dust? man delights not me: no, nor woman neither, though by your smiling you seem to say so.
More recently, in the 20th century, the phrase 'a real piece of work' has been coined to mean 'a really bad person, lacking morality and scruples'. This goes further than Shakespeare's usage which, while appearing to glorify man, is ironic in suggesting that man is very far from a masterpiece.
See other phrases and sayings from Shakespeare.