In The End — There can Be Only Two.
The Chymical Wedding
Always Two, There Are -
No More, No Less.
A Master, and An Apprentice.
And an Applicant.
Which Shall Be Destroyed...?
The Master, or The Apprentice...?
Or The Applicant..?
Three Men Enter - Two Jedi, One Sith
Three Men Leave -
One Jedi, One Sith, One Sith/Jedi
•WISH GRANTED•
Clearly, you can't.
Dooku never got this far —
He had to renounce The Jedi Order in order to claim his hereditary title of Count on his homeworld, and he never made it onto The Jedi Council -
So he was never a Jedi Master and a Sith Lord
at the same time
Vader is A Jedi Master/Sith Lord who decides to serve Evil
(Because he thinks his wife and child are dead and there is nothing to live for)
Luke is a Sith Lord/Jedi Master who decides to be Good
(In order to redeem his Father)
This is Balance.
But then his father dies -
This is a problem...