User blog comment:BellatrixTheMagicalPotato/Why Voldemort Would Easily Kill Vader/@comment-4840996-20150603093720/@comment-26531114-20150603111154

Vader wouldn't even know about magic, therefore he might think the wand was just a fancy stick. Also, Voldy can easily implant false memories into a person's mind of force them to relive their worst ones. Also, one simple reducto curse, and Vader's lightsaber would be just a few shiny scraps of metal. Voldy would also be able to easily distract Vader with fancy sorcery.