full dark side is never a good idea, to justify my currently dark leaning knight i started him as a tribal straight from rattatak who slowly started embracing jedi ideals during the plot until the end of act II when he started falling, but instead of savage kind of falling he started becoming colder and more judgemental, until he killed a certain corrupted guy on corellia, he then killed the final boss and is getting more ruthless by the day.
i'll not turn him into a drooling dark side psycho, more like a merciless hero.