You killed her because finally, when you could have saved her, when you could have gone away with her, when you could have been thinking about her, you were thinking about yourself. It is in this blazing moment that you finally understand the trap of the Dark Side, the final cruelty of the Sith, because now, yourself is all you will ever have. and you rage and scream and reach through the Force to crush the Shadow who has destroyed you, but you are so far less now than what you were, you are more than half machine. You are like a painter gone blind, a composer gone deaf. You can remember where the power was, but the power you can touch is only a memory. And so with all your world destroying fury, it is only droids around you that implode, and equipment and the table to which you were strapped shatters, and in the end, you cannot touch the Shadow.