3. Obi- Wan Kenobi Not Killing Darth Vader In Revenge of the Sith
After a long and epic duel, Obi-Wan Kenobi has Darth Vader beat. He can end it all and defeat the Machiavellian villain. Yet the child murdering, Jedi Temple desecrating Sith Lord is spared by old Ben. This is a huge miscalculation. Obi-Wan must have known, perhaps using some kind of Force, that he would never get another chance like this one. He could have stopped the continued slaughter of Jedi under Order 66, and ultimately saved the billions killed with the Death Star. While the counterpoint to argument is that Anakin did end the Sith and bring balance to the Force. Did he? No. There are stacks of SWEU novels and games that take place after Vader. Anakin didn't even kill the Emperor enough for him to stay dead, see the Dark Empire Trilogy. There is no argument in favour of Obi-Wan's screw up on Mustafar. Just a bunch of really bad results.