Whatever criticisms of the prequels, Anikin certainly took a long while to turn to the dark side. Of course how well that transition was done is another matter.
Oh well the answer to that is simple. Daemons. There were no daemons in Star Wars you say? I mean the greater daemon Georgus Lucophorus the Mad who feeds on the tears oft Star Wars fanbois.
That better not be an actual spoiler! 1. I thought so! 2. You B*$£*%d! 3. Who else here wants perform Exterminatus on the Krogan? Hands up. *Raises hand.*