He had no choice...
If Anakin wanted to save Padme there was only one man who could help him. The Supreme Chancellor of the Republic, Chancellor Palpatine.
But Palpatine, a close friend of Anakin, was also the very sith lord they had been hunting for years. Palpatine was evil, a perversion of the Force...
And yet, he was the only one who could save Padme.
Yoda had meditated with Anakin, and had told him "You must learn to let go that which you fear to lose."
This was a teaching that would never satisfy Anakin Skywalker. He had lost his mother. He would not lose his wife and child.
So, in Palpatines office, faced with a choice between helping the distrustful Mace Windu or his powerful friend Palpatine he chose the latter, and swiftly pledged his allegiance.
But did he truly mean it?
Anakin had been seeking out the sith lord for long months, and now he knew who it was, and what he could do for him he joined him. The Jedi were liars in Anakins eyes. He felt they had treated him badly and held him back, lied about many things. But Paplatine was always clear and true to his word.
And yet Anakin knew that his powers were devloping swiftly, and that after he had learned all he needed from Palpatine that apprentice would usurp master.
On the Mustafar landing platform Anakin made clear his intentions. Together, he and Padme would defeat Palpatine and rule the galaxy.
Sound familiar?
Anakin believed in the kind of `democracy' that Palpatine was peddling - strong rule with a firm hand. It was a way of thinking that he, as Darth Vader, would practise and preach.
But Palpatine would have known that his apprentice harboured these thoughts. Perhaps that's why Vader was often sent away for extended periods of time on important missions, away from Coruscant. Perhaps Palpatine knew that Vader was a constant threat to him, and treated him as such.
Between the events of Star Wars and Empire, Anakin learned that the pilot who destroyed the Death Star was his son, Luke Skywalker.
The child who Palpatine had said was killed, by Vaders own hand, along with his mother on Mustafar.
Now Vader knew Palpatine was a liar, but he was too deeply emerged in the Dark Side.
Or was he?
He offered Luke the chance to destroy the Emperor and rule the galaxy as father and son.
This was no hollow offer - Anakin meant it. In many repsects, Empire was the only time we really saw Anakin verbally formalise his intent to fulfill the Prophecy of the Chosen One.
But Luke rejects him.
And yet the path is set, and in Jedi, after seeing enough he carries out his destiny.
So, given his intitial intention to defeat Palpatine and rule the galaxy, just how loyal was Anakin to Palpatine?