One of the signature powers of the Sith seen throughout various Star Wars media is Force Lightning, so it seems odd that Darth Vader, the greatest wielder of the Dark Side, never used it. In the past, the common explanation has been that it cannot be channeled through his robotic limbs, but it has now been explained that Vader possesses the power, but it’s too dangerous for him to use, with it coming down to his lightsaber.
The red blades of the Sith are created through a process called bleeding, where a Dark Side adept pours all their hate, anger, pain and resentment into a lightsaber’s kyber crystal, the corruption turning it crimson and bending it to the user’s will.
As seen in the 2017 comic series Darth Vader: Dark Lord of the Sith, soon after his rebirth, Vader traveled to an isolated moon to hunt down Kirak Infil’a, a Jedi master who survived Order 66, for his weapon, as the Sith believe lightsabers should be taken rather than bestowed or created. He’s almost defeated by the powerful Jedi though, only triumphing by exploiting the Light Side warrior’s compassion for innocent life.
What occurs during bleeding is seen in the current ongoing series Darth Vader, with the Sith Lord commanded by Sidious to travel to Mustafar to perform the process, it being a focal point for Dark Side forces. While summoning the abyssal deaths of his negative emotions, he also calls powerful lightning as he’s haunted by memories of everything he’s lost and destroyed to reach this point.
The nigh-apocalyptic fury with which the elemental power is unleashed almost destroys the entire planet and himself along with it. Despite nearly being driven insane by the visions he receives, the process is successful, but evidently leaves Vader with an aversion to ever again use the electrical might that his cohorts are more than willing to cast on a whim.
Even without the use of Force Lightning though, Vader has many times been seen to be more than a match for almost any fighter he encounters whenever he appears throughout the Star Wars canon, his peerless skill with the red blade being chief amongst them.