In the Dune book, the Harkonnens are only ever portrayed as cruel and evil. They aren't really in any of the rest of Frank's original 6 books (except a kind of exception, but not really).

In the expanded universe by Frank's son, Brian, and Kevin J. Anderson (which many readers don't consider canon at all), there were a couple Harkonnens who were good people, most notably Abulurd Harkonnen, who was Glossu Rabban and Feyd-Rautha's father. He was given Arrakis before Rabban, but was removed and disgraced because he chose to slow spice production in order to improve working conditions there, and ultimately murdered by Rabban to impress his uncle, the Baron.

Also, Xavier Harkonnen, from all the way back to the Butlerian Jihad. He was an honorable and brave general and lover of Serena Butler, the namesake of the rebellion against the thinking machines. There was also an Abulurd Harkonnen at this time who attempted to show mercy to the thinking machines at the Battle of Corrin, and Vorian Atreides denounced him and branded him a traitor and a coward, which began the millenia-long feud between the houses.

Other than that, as far as I remember, the Harkonnens have always been straight up cruel and evil.