Obsessed with the prospect of eternal life and ideas of spontaneous regeneration, as he remained focused on matters of the material world, though in later years Darth Vader mused that Plagueis had also desired a way to preserve the immaterial self after the death of the body. Typical of a...
Well, Exar Kun subdued Luke in the form of a spirit. In addition, a powerful Dark Jedi also outclassed Luke in single combat (Interestingly, Luke was already incredibly powerful at this point). These events indicate that powerful dark side practitioners can hold their own in combat situations...