"Obi-Wan is staggering at the edge of a railing having been beaten back by the powerful Vader. He looks into the eyes of the black Sith warrior's mask and solemly says " What have you become? You were once Anikan Skywalker, the proud and courageous Jedi. You were once my friend. Please come back to the light." Vader leans in and runs him through with his crimson blade, and quietly states in a mocking tone.
"You fool, I destroyed your apprentice. I offered him mercy if he would but join me. He said no, so I took the power and life he would not use." Obi-wan stares at Vader not knowing how to react. All he thought he knew was a lie. Vader was not Anikan, who could be turned back to the light and over throw the emperor, he was just a monster. A monster who could not be stopped. Unless, unless, yes he could do it, but where to find him? Only the force knew. So trusting the force Obi-Wan smiled, and slowly said. You may not fall by my swored Vader, but you will fall by a sword stronger than evn you or your masters. You will stare into the eyes of the very force you have for so long tried to crush. The light always wins. And with that Obi-Wan lets the life leave his body and he plungs over the railing and into oblivian.
Obviously it needs some work but it is just an idea.