I'm assuming you're talking about the bit where you face Kyle across a phantom platform. Turn around and step off of your disc into the void. You'll be teleported to another disc in another room. Then turn off your lightsaber, step off the new disc, and the ending cinematic should play. It's one of those Jedi nonviolence things. Kind of out of place given the nature of the rest of the game, but I guess that's why I don't work for LucasArts.
I am the storm of night, the wall of skulls, the razor's song, the tide of horror, the cacophony of death. My name is Darth Umbra, and I am that which you fear.