Ugly for Ill-natured, Quarrelsome. What is ugly is the temper, or disposition, not the person having it.
Under-handed and Under-handedly for Under-hand. See Off-handed.
Unique. "This is very unique." "The most unique house in the city." There are no degrees of uniqueness: a thing is unique if there is not another like it. The word has nothing to do with oddity, strangeness, nor picturesqueness.
United States as a Singular Noun. "The United States is for peace." The fact that we are in some ways one nation has nothing to do with it; it is enough to know that the word States is plural--if not, what is State? It would be pretty hard on a foreigner skilled in the English tongue if he could not venture to use our national name without having made a study of the history of our Constitution and political institutions. Grammar has not a speaking acquaintance with politics, and patriotic pride is not schoolmaster to syntax.
Unkempt for Disordered, Untidy, etc. Unkempt means uncombed, and can properly be said of nothing but the hair.
Use for Treat. "The inmates were badly used." "They use him harshly."
Utter for Absolute, Entire, etc. Utter has a damnatory signification and is to be used of evil things only. It is correct to say utter misery, but not "utter happiness;" utterly bad, but not "utterly good."