dokuu busts out the force lightning on anakin (as well as cuts his hand off) in AOTC. this is VERY VERY VERY important. GL does this for a very specific reason.
Remember in ROTJ at the very end, Luke gives way to anger and strikes down his father, Vader. He cuts his hand off. this is the SAME HAND Dokuu cuts off in AOTC. Then the Emperor uses force lightning on Luke. Anakin watches his son in agony. the SAME agony he once endured. you see Vader LOOK AT HIS MISSING HAND, he is remembering the experience he had on genosis. Anakin saves his son, kills the emperor, and turns back to the good side.