How about paskudnyak? It’s in Leo Rosten’s The Joys of Yiddish, and he defines it as “a man or woman who is… nasty, mean, odious, contemptible, rotten, vulgar, insensitive, petty and — in general — opprobrious” — in fact, the diametric opposite of a mensch. I like it because it sounds like what it denotes, and it’s a great name for a character in a joke or a parody: “Mr. Paskudnyak, welcome to Let’s Make a Deal!” I’ll be sorry if it isn’t in common usage at least in some circles.