Please note that this comp will count small factoids from the old Star Wars Expanded Universe that have not been explicitly contradicted by new canon or debunked by word of the content creators.
I personally liked the decision to put the old EU in its own continuïty and will have a civilised discussion with anyone who attempts to convince me otherwise.
Darth Vader was 44 years old at the time of his death, but the actor portraying him, Sebastian Shaw, was 77 years old at the time of filming.
Fans often attribute Vader's old appearance to his severe injuries and a lifetime of using the Dark Side.
In Star Wars Infinities: Return Of The Jedi, a What if?- comic, The redeemed Anakin instead survives the Battle of Endor due to both Luke and Leia being aboard the Death Star, and joins the Rebel Alliance wearing a white version of his Sith Armor.
As the Chosen One, Anakin was basically destined for godhood, and at full power, no being in the Galaxy could remotely compare to him, not even such prodigies and masters like Yoda or Darth Sidious.
When Anakin found himself stuck on Mortis ( a planet tied strongly to the force) during the Clone Wars, he forced the living representations of the Light and the Dark Side to their knees with his strength in the Force.
After losing most of his living tissue and suffering a severe mental breakdown following the battle on Mustafar, however, Vader possesed only a tiny fraction of his true power in the force.
It should be noted, however, that a tiny fraction of near-infinite power still amounted to one of the strongest Sith lords and Force users to have ever lived. Amongst Vader's known feats are:
-Force-Choking someone from across the Galaxy,
-Defeating a massive Rebel army, including Air Support, after they surrounded him.
- Toppling an AT-AT walker meant to crush him twice/
- Using Animal affinity and the Mind Trick to force a gaint cyborg Space Whale to fly itself into a sun.
George Lucas himself has stated that if the Emperor's Force Power were a 10, Darth Vader's Force Power was an 8.
As Anakin, Vader preferred to use the most offensive and acrobatic Lightsaber form, Ataru (form IV). As Vader, he instead used a Hybrid fighting style incorporating elements of:
1) Soresu (Form III, pure defense)
2) Makashi (Form I, purely Duel-centric)
3) Shien/Djem So (form V, counterattack-based combat against blasters and Lightsabers, respectively)
Vader employed this custom style to account for the extra weight and vulnerabilities of his suit, although if the situation called for it he would supplant his speed and agility with the force and use his old Ataru mastery.
Vader was one of the most refined and lethal duelists in lightsaber combat history, and in canon almost never lost a fair fight. He:
- Overpowered an adult Ashoka Tano and forced her off a cliff before she later on took him by surprise
- Bested Kanan Jarrus and Ezra Bridger at once with one arm while trying to let them win .
- Was so strong Maul did not even want to consider dueling Vader, much less alone.
- Bested an arsenal of Cybernetically-enhanced Lightsaber duelists the Emperor sent after him.
In Legends, Vader was still powerful, but not quite as infallible and lost several major battles.
Darth Vader's life support suit was based on the designs used for General Grievous, although Vader's Armor was much cheaper and more uncomfortable than Grievous' armor. It pulled and shafed his tender flesh, had a chest plate that kept Vader from raising his arms above his head, and was slow and cumbersome. Vader also had little to no sleep while wearing the armor, because the sound of his iron lung breathing for him kept him awake at nearly all times. At length however, Vader managed to find some peace in the sense of isolation his suit gave him, and its uncomfortable and painful nature made it easier for Vader to draw upon the power from the Dark Side.
In legends, Darth Vader could never leave his suit and had to periodically scrub his body to prevent infections and necrotic flesh.
In Canon, Darth Vader can have small moments of reprieve and enter a Bacta Tank.
It was by the Emperor's will that Darth Vader had his castle placed on Mustafar.
Fans joke that Darth Vader insisted the castle be made as high as possible.
Darth Vader actually had no formal rank in the Empire, but as the Emperor's personal servant any order from him was to be considered an order from the Emperor himself. A select few, such as the Emperor's personal guard and Grand Moff Tarkin, could ignore Vader's commands at the Emperor's behest.
Darth Vader's suit actually has subtle differences in every installment, primarily the chest plate.