Damn near impossible to tell. But if you take the statement that he is the most powerful Jedi Vader has faced up to that point in time seriously, then he gets to at least 4.
He did nothing to suggest he was above Obi Wan kek
__________________ "Happiness is a lie. Life is horror. The light is always dying all across the universe. The last star will flicker out someday, when it does, all that remains is shadow. And I will be its king!"'-Amahl Farouk
As of Mustafar, Vader is still labeled as ANAKIN. Meaning Kirak is the most powerful Jedi SUIT Vader faced. Not Knightfall or Mustafar Anakin.
That being said, should stop at TPM Maul.
__________________ "Once more, the Sith will rule the galaxy! And... we shall have... peace."
Actually, he's still considered as Anakin, Vader is, we could say, a formality at this point, and he will take his first steps as Darth Vader after the suit operation,
"When Anakin Skywalker fell, both to the pull of the dark side and to the blade of Obi-Wan Kenobi, he rose back up, more machine than man. Having lost everything that was once dear to him, the former Chosen One must take his first steps into a darker world... As Darth Vader."
Star Wars Darth Vader: The Chosen One Part 1
__________________ "Once more, the Sith will rule the galaxy! And... we shall have... peace."
It's almost like they are the same character. :shock:
The idea that Anakin and Vader refer to separate beings is ridiculous and misses the point of the saga. With that said, I think the blurb or whatever is non-canon and irrelevant.
The "opening crawl" of Vader 1 labels him as Vader when he fights obi wan.
"Jedin knight Anakin Skywalker has fallen to the darkside of the force. Swayed by Palpatines promise to help prevent the death of his pregnant wife padme, Skywalker betrayed the Jedi and became the sith lord Darth Vader. Defeated by his old friend and former master obi wan kenobi, Vader was left to die on the volcanic planet Mustafar. "
According to the bibliography of Vader released earlier this year, Anakin died on Mustafar as per Vader. So Knightfall and Mustafar are considered him.
__________________ "There is only Revan. Only he can shape this galaxy as it is meant to be shaped."