The phrase "a nasty man" is correct and usable in written English.
It can be used to describe someone who is unpleasant, mean, or morally reprehensible.
Example: "Everyone in the neighborhood knows that he is a nasty man who treats others poorly."
Alternatives: "an unpleasant man" or "a mean-spirited man".
For that matter, he is not even a nasty man.
Here was a nasty man who somehow wrote sublime and stirring operas.
For it does not matter if he was a nice man or a nasty man.
I'm a nasty man, a no-good leader when I began to speak," he complained recently.
In the temporarily occupied quarters on Broome Street, Leon Golub's 1986 painting of two elderly black women with a nasty man in cowboy boots still exudes an appalling beauty (Johnson).
Former Mayor Ed Koch, who has written an entire book describing Mr. Giuliani as a "Nasty Man," noted pointedly that the mayor had done an excellent job and that "some flawed people, in extraordinary times, lose their defects".
He could not get through a story about "a really nasty man" — an Irish priest who sexually abused, physically tortured and emotionally threatened vulnerable boys — without pulling out his handkerchief and wiping his nose.
Sir Francis Galton, begetter of the eugenics movement, was a thoroughly nasty man in many ways, and it's certainly reasonable to quote his many racist remarks.
"A very nasty man has just tried to kill us all," one of the passengers, Benjamin Goldsmith, quoted the captain as saying after the plane was back under control and the assailant subdued.
We were the ones who forced a peace treaty on the people of Sierra Leone that gave one of the world's premier war criminals -- an exceedingly nasty man named Foday Sankoh -- a cabinet position, control over Sierra Leone's diamond mines and the license to take over the country by force.
It happened because of the collapse of a noble who, amid tough competition, was an outstandingly nasty man.
