Force lightning required a living conduit for the energy to be channeled; thus Darth Vader, despite being an immensely powerful Sith Lord, was never able to properly employ this ability, as any attempt to generate it carried the risk of shorting out his life support systems.

Is Vader weak to Force lightning?

19 Weakness: Electricity

Darth Vader possessed the skill to use Force lightning, but the limitations of his suit prevented this. A lot of the systems that were keeping Darth Vader alive were maintained by electricity, which is why Force lightning was so destructive towards him.

Can Force lightning be blocked?

Seasoned Jedi can even use their lightsabers to block attacks of Force lightning generated by Sith Lords." According to Luke Skywalker, there's a sense of progression to this; only the most seasoned and capable Jedi Masters can deflect Force Lightning.