He was portrayed by Kenneth McMillian in the 1984 film and Ian McNeice in the 2000 Sci Fi Channel (now SyFy) miniseries.
In 10,191 Harkonnen and Emperor Shaddam IV devised a plan to rid themselves of the Atreides. The Emperor made the Atreides move from their home on Caladan to the planet Arrakis, to take over operations on that planet, which was the only place known in the universe to produce spice. On Arrakis, with the aid of the Emperor's Sardaukar troops, Duke Leto was killed, the Atreides forces were scattered, and Leto's wife Jessica and son Paul were forced to flee into the desert.
After encountering the Fremen Paul and Jessica joined with them, and Paul became known as Muad'Dib. Paul led the Fremen in a war against the Harkonnen and brought spice production to a standstill. This brought the Emperor and all the Great Houses to Arrakis. Baron Harkonnen was killed by Paul's sister Alia via a Gom Jabbar (in the 1984 film, in addition to poisoning the Baron, Alia also shoved Harkonnen telekinetically outside the palace to be devoured by a sand worm), and Paul forced the Emperor to give up his throne so that he could assume the throne for himself.
Even death of his body was not the end. Because Alia had been exposed to the Water of Life prior to being born, she was susceptible to the spirits of her ancestors, including her grandfather. Her grandfather manipulated her into acting against her only family, only to be stopped when Alia committed suicide to put an end to her grandfather's activities once and for all.
The Baron was well known for his sadistic tendencies. In the 1984 fim, a favorite activity of his was to pull out the heart plugs of young men, which became a way of achieving sexual satisfaction.
Harkonnen was an incredibly cruel man who had no problem with using murder, slavery, and torture to maintain and increase his hold on power. These traits gave the House its notorious reputation and led to an increase in the popularity of the Atreides amongst the other Houses and the population of the Empire.