A miscreant is a person who is bad––who lies, breaks the law, yells at small puppies. It's a somewhat old-fashioned word, popular with old ladies shocked at having their purses stolen at the opera.
Miscreant, like lout, lecher, good-for-nothing — they're the words proper people use to condemn the improper. Improper people consult an entirely different thesaurus of condemnation, perhaps familiar to you but not possible to quote from in this PG-rated word blurb.
