There's A Reason Why Darth Vader Never Uses Force Lightning
Force lightning is something that has been a part of "Star Wars" since the original trilogy. We have seen Sith use it against their enemies dating back to Palpatine in "Return of the Jedi." Ever since then, it has appeared in just about every project in the franchise that involves the Sith. That begs the question, why don't we ever see Darth Vader, the most notorious user of the dark side of the Force in a galaxy far, far away, ever use this powerful ability? While Lucasfilm has never explicitly said why he hasn't or that he can't, the official canon appears to be hiding the answer in plain sight.
What is Force Lightning and how is it used?
First, let's go over how Force lightning is officially defined by the official "Star Wars" canon. To do that, we are going to share the official StarWars.com database entry on the ability, which offers a simple but important explanation of how the power is used, which is key when it comes to understanding why Darth Vader can't use it. Per the website:
"Force lightning is a dark side ability used to torture, disfigure, and even kill one's victims. Blue in color, Sith shoot Force lightning from their hands by calling on their hatred and aggressive feelings. However, while a deadly weapon, it is not unstoppable. Force lightning can be deflected and absorbed by a lightsaber, and select Jedi have proved able to neutralize the technique through the power of the light side."
Before digging into the reason, be sure to remember that the folks at Lucasfilm specifically say that Force lightning is channeled from the hands, and also not the mention of the "light side" as that may come into play here as well.
2017's Darth Vader #8 holds the key
Writer Charles Soule and artist Giuseppe Camuncoli contributed a great deal to the mythos of Vader in the 2017 "Darth Vader" comic that ran for a total of 25 issues. But the moment in question as it pertains to the character's lack of Force lightning use came in the pages of "Darth Vader" #8, which was published in November 2017. The issue sees Vader and the Inquisitors hunting down Jocasta Nu, one of the last remaining Jedi in the aftermath of Order 66. The issue takes place very early on after Anakin Skywalker was left for dead on Mustafar by Obi-Wan Kenobi at the end of "Revenge of the Sith," still transitioning into his new life as Vader.
Marvel Comics
At one point, we get a page that occurs as Darth Vader is lost in thought, seemingly meditating and connecting to the Force in some way during a quiet moment. The above page shows us a version of Vader's likeness within the Force, with red, a color commonly associated with the Sith, running through his body, save for his arms and legs, which are white. Why is that? Well, Vader lost his extremities on Mustafar and they are now mechanical. And therein lies the answer.
Sith specifically channel Force lightning using their hands. Seemingly, because Vader's hands are no longer there, he can't channel the dark side of the Force through them, meaning that he can't use Force lightning. Beyond that, we see those blue butterflies, which seem to signal at least a bit of conflict with the light side of the Force. And the light side can "neutralize" Force lightning. With that, it seems this is one ability that the fearsome Darth Vader simply doesn't have in his tool belt. Back to choking people out for their incompetence.