Darth is the balance in The Force. Most of people didn't paid attention to the whole saga, especially the scene when Vader asked Luke to join him... he literally said "join me and we will bring balance into The Force".

Many viewers of Star Wars saga, think that Darth Vader was the “bad guy”.

I suggest you all watching again the whole series and focus on all Vader’s actions and words. He was actually The Balance into The Force, he was forced to join (briefly) with Emperor Palpatine, in order to bring down the Empire. His main goal was peace and be with Amidala… Palpatine fooled him into believing that if will join to the Sith it could bring Amidala back. Was a lie. He knew also about the “other side” of the Jedi.

The whole story of Vader is that he loved so much Amidala. He was deceived by Palpatine and he realizee it when Palpatine put him in the Vader costume. He NEVER joined the Sith... was just tricked to be bad...

The Jedi and The Sith are just the today’s “left and right” political sides.

Darth Vader wanted Luke to join him into bringing down both sides and finally have The Balance into The Force. Think again why Luke Skywalker after Vader’s death decided to isolate himself. He realized the mistake he did for not joining forces with Vader.