Yoda and Obi Wan wanted Luke to kill Darth Vader and the Emperor. What makes no sense to me is that they wanted Luke to kill Palpatine. When Yoda was training Luke on Dagobah, we never saw Luke being trained in combat. Yoda never taught Luke about Force duels, or how to use the Force against your enemy in a fight. And most of all, neither Yoda or Obi Wan warned Luke about the dangers of the Emperor's force lightning. How in the world would they expect Luke to defeat Palpatine? Yoda said "Only a fully trained Jedi knight with the Force as his ally will conquer Vader and his emperor." Luke was never warned about the Emperor's force lightning, or how to duel such a powerful Sith. Obi Wan wanted him to kill Vader, and that means that he also wanted Luke to kill the Emperor too. He had no faith in redeeming Anakin, so he obviously expected Luke to do the job of killing Palpatine. Luke told Leia, "If I don't make it back, you're the only hope for the alliance". Leia received no force training whatsoever. And they expected Leia to defeat the Sith? At least Luke was trained as a Jedi, Leia wasn't. She doesn't even seem powerful enough to defeat Vader, let alone Palpatine.