Star Wars POTF - Darth Vader

The greatest baddie in the Universe - Darth Vader, Lord of the Sith

Prior to Episodes 1-3 he remained an enigmatic character, incredibly powerful and evil, yet finally turning back to good.  Now we know far more about the fall of Anakin and the rise of Vader.  He had the potential to be one of the greatest Jedi Knights the Republic had ever known, but anger, arrogance and resentment pushed him to the Dark Side.  The fires of Mustafar destroyed his body and gave rise to his iconic look.

It is odd to note that one of film history's greatest villains was, in fact just the sidekick to the real villain - Emperor Palpatine.  On several occasions Palpatine betrayed Vader in attempts to replace him with a new apprentice.  The damage caused on Mustafar weakened Vader physically and reduced his abilities to use the force.  Palpatine searched for replacements for Vader but through mutual betrayal and mistrust the two were forced to work together.

The final redemption of Vader and his passing from a physical body into a spiritual one as seen at the end of ROTJ demonstrates how the Sith were always doomed as the most powerful secrets of the Force could only be unlocked through love.  This theme is of course revisited in the Harry Potter books through Voldermort's failure to kill Harry.