this is a disclaimer.
by a burning brook
Vader has not felt such anger in a long, long time.
The Sith speak of giving your emotions free reign, of indulging your darker passions, but that is just the beginning. In truth, the Darkness is cold, and empty as space itself. Before Kenobi's betrayal, his fury burned like fire, but that was a long time ago, and now there is nothing but cold, snakelike malice and the vicious, but oddly quiet, satisfaction of destroying his enemies.
Leia Organa, however, makes him angry. Her betrayal makes him angry (almost as angry as Kenobi's), her anger provoking, her temper defying his own. He has always known she was a Force sensitive. Although his Master, curiously, never saw it himself (and Vader never saw a reason to mention it to him; knowledge is power, after all), the constant possibility of her execution has kept Bail Organa relatively well in line for over a decade.
Now, Vader almost wishes she were trained. He has not duelled a Jedi in several years now, and he cannot help but think that Leia Organa might almost be a match for him.
Make no mistake: she has always despised him, and the feeling has always been mutual. But always before it was an oddly cordial abhorrence, undercurrents of something like respect running through it. She has no more time for the schemers and the intrigues of the Court than he does, cutting through them with words she wields as deftly as she would a lightsabre. More than once he has quietly given his support to one of her motions – to destroy one of his own enemies, to increase efficiency or cut back on the bureaucracy that chokes not only the political system (that he does not care about) but also the military (which he does).
And now she has proven herself a Rebel and a traitor. The discovery of that secret truth to Leia Organa makes Vader angry in a way that nothing has since Kenobi himself, waking a black fury that loosens his own sharp tongue and his temper both, destroys his hard-won patience and nudges emotions into life that Vader had believed he no longer had. Leia Organa, frankly, makes him feel
(almost like Anakin burning bright and full of life all the cold and the deadness swept away)
and that, perhaps, is what makes Vader angriest of all, and so he does not hold back when he arrests her, executes her whole crew, watches her interrogation as though she were nothing and no one (she is nothing to him!), and knows, when she looks at him, that she feels as betrayed by him as he does by her.
(What did she think she could do to stop Tarkin: claw his eyes out? Better to die gently, quietly, by the needle, than be shot down by the troopers at the doors.)
Her friendship with his son feels oddly fitting; at Bespin, he has no need to torture her. Her fear for Solo and her strength in the Force will be more than enough to bring Luke to him.
Vader wonders briefly if Luke loves her, but dismisses the notion almost as soon as it occurs. Jedi don't love. Kenobi would have taught him that. Still, she doesn't even realise she's reaching out to him; the connection between them feels as natural as
(Kenobi and Skywalker, inseparable and unbeatable)
any that Vader has ever sensed before.
He feels a grim satisfaction when he tells Luke the truth (mine, you are my son, Kenobi has taken all the rest from me but you I will keep, my child and hers) and agony like nothing it seems in your anger you killed her before when the boy drops off that cursed ledge. Leia Organa recedes to the back of his mind, except for an occasional worry that Luke is training her, that soon they will have two Jedi to contend with.
But interesting that despite his Master's demands that he track down (kidnap capture) his son and turn (destroy) him, the Emperor still does not concern himself with Leia Organa.
For the first time, Vader wonders why he does not simply tell the Emperor about her. Any possibilities for gaining an advantage in keeping her secret have long since passed; if she can be influenced, she may influence Luke in turn.
Nevertheless, he holds his tongue, and searches for his son.
It is not until he stands before his Master in the throne room of the second Death Star and understands that for all his power the Emperor cannot sense Luke the way Vader can that the man who was once Anakin Skywalker begins once more to see a glimmer of another, deeper truth to Leia Organa.
But this time it fails entirely to anger him.