9. Exar Kun
Exar Kun was an influential character both as a living person during the Old Republic and as a Force Ghost during the New Republic. During his life, he was a very arrogant person, a trait that was undesired by the Jedi Council. His thirst for power had consumed him so much that he opened the tomb of long-deceased Sith Lord Freedon Nadd. In doing so, his downfall truly began, and he proceeded to corrupt many Jedi. Upon slaying his former Jedi Master and many others, he began a reign of terror to satisfy his thirst. It was not until his imminent capture by the Jedi that he somehow managed to split his spirit from his body, using an ancient Sith technique. His spirit would torment future Jedi, especially a Padawan named Gantoris. However, his spirit would later be vanquished by the combined power of numerous Jedi, including Luke Skywalker and the spirit of his former Jedi Master Vodo-Siosk Baas. Indeed, Exar Kun was an early example of the behavior that consumed Palpatine; his desire for power above all else branded him an enemy of the established order in the Galaxy, and even in the afterlife, his spirit would be consumed by the need to control and to usurp power.