ugly customer

beat with the ugly stick

Used to describe someone who is particularly ugly or unattractive.

fall out of the ugly tree and hit every branch

To become extremely unattractive.

ugly American

An American government representative, tourist, or businessperson who, in dealing with people of other nations, is haughty, rude, meddlesome, chauvinistic, or jingoistic.

ugly duckling

A young person who is ugly, but who is expected to become beautiful or handsome as they mature.