In Revenge of the Sith, Palpatine failed to kill Yoda after the Jedi Master escaped the villain's wrath. Now, it's been revealed that Darth Vader nearly reminded his Master of that in Obi-Wan Kenobi.
Obi-Wan Kenobi movie writer Stuart Beattie has revealed that his big screen take on the story was set to wrap up with Darth Vader believing he had defeated and killed his former Master. Check it out.