Oh, I know it's not about just Force lightning. My post five entries earlier mentions more than just his abilities to throw lightning like other Sith Lords. After his near-death experience on Mustafar practically everything about him was weaker and less impressive. Combat skills. Speed. Agility. Strength with a lightsaber. He was a shell of his self when he was still a Jedi Knight and still Anakin Skywalker. Only in the realm of psychic and psychokinetic Force powers was he stronger, and that was largely because his confinement to the black life-support armor and transformation into not much more than a machine left him few other avenues where he could surpass his old skills when he was still mostly human. He spent the next generation focusing on and refining those powers because as a swordsman and warrior he was slowed and hobbled with no chance of regaining the athletic glory of his youth.