What if Anakin Killed Obi-Wan on Mustafar?

In Revenge of the Sith, we witnessed Anakin and Obi-Wan’s nail-biting duel on Mustafar and how Anakin was eventually defeated by his old master. As a result, he was burnt so badly he was then forced to live the rest of his life in pain and suffering.. but what if he was the one to defeat Obi-Wan instead of losing to him?