This is a great question. Of late, there have been many more African Americans who are the heroes. This shows that there has been a change in society. However, there are movies where the villains are African Americans. Let me list a few of them.
Perhaps the most famous recent movie is American Gangster, where Denzel Washington plays the role of Frank Lucas, one of the most notorious gangsters in New York history.
Another example is the movie the Last King of Scotland. Forest Whitaker plays the role of Idi Amin, the brutal dictator of Uganda. This was a disturbing film, which portrayed abject evil. Whitaker won the Oscar for his performance.
One more example will suffice. In the movie, New Jack City, Wesley Snipes plays the role of a notorious drug dealer, Nino Brown. From the beginning of the movie, he has no redeeming quality.
For others, consider: Training Day with Denzel Washington and Rocky III with Mr. T.
Kingpin (in Daredevil film, Marvel Comics) Elijah Price / "Mr. Glass" (in Unbreakable) "Mr. Range" (in Super film)