Vader did the equivalent of a sucker punch to Sids - he snuck up from behind, grabbed him and tossed him down a shaft..barely. He fell to his knees immediately after letting go of Sids. This only shows Vader had to get Sids while distracted b/c if not Sids would have fried him into a piece of burnt toast. May I remind you that when Vader was picking up Palpatine to toss him down the shaft, the latter was in the process of using Force lightning? Gee, I guess that's why Vader ended up being affected. And may I ask this question? If the loss of limbs had diminished Anakin's connection to the Force, why did he become more powerful after losing a right arm to Dooku's lightsaber in AOTC?