4. Adelei Niska
Niska, played by Michael Fairman, is the psychotic crime lord who appears in two episodes of Firefly (The Train Job and War Stories). Niska is such a great character because he is a constant formidable force in the face of Mal and company. He is an actual threat, powerful and sadistic, willing to torture Mal and Wash during War Stories and even cutting off Mal's ear. His first appearance cements his reputation by showing a bloody body hanging from the ceiling a corpse later to be revealed as his wife's nephew, who failed to complete a job. Niska hires Mal to steal crates from an Alliance train but when the crates are revealed to hold medicine, Mal refuses to complete the heist. In not completing the job, Niska is left seeking revenge which comes about in the tenth episode of the series. If the series was to continue, I am sure that Niska would have recurred many more times. Having portrayed a true threat to the crew, he is extremely memorable supporting character because of his brutal displays of punishment and even has his own soundtrack, played on the dudek, that gave his scenes a distinct feel.