I also don't think Yoda or Obi-Wan think Anakin can be redeemed. Yoda: "Destory the Sith we must!" Not redeem the Sith or Anakin/Vader. Redeeming Vader is what destroys the Sith. Luke couldn't have destroyed Palpatine. If Yoda and Ben wanted Vader dead, then why is the cave on Degobah a failure? I can't for the life of me remember who first posted this question to me on this board, but it completely changed my opinion about Yoda and Obi Wan's intent on Anakin. If it was a matter of Luke killing Vader, why not encourage Luke to kill Vader in the starship battle at Yavin IV? They knew that Luke confronting Vader would end up with Anakin's death, not that Luke would kill him. That Vader would take out the Emperor on top of that only proves that Anakin is the one of the prophecy. As I've often said, Anakin is both powerful and at one point, a Jedi, but is not a powerful Jedi until he casts the Emperor down the shaft.