In watching the original trilogy, it is often hard to really get an understanding of the conflict within Vader. Luke noted that he could sense the good in him. But I couldn’t sense the good in him when watching those films. The new canon, however, has provided some better fodder for better understanding Vader’s character during the original trilogy.
“The son of Skywalker must not become a Jedi.” ~ The Emperor in The Empire Strikes Back
This was a very strange way to address Darth Vader, but it does make sense. It establishes that Vader does not identify with his former self. But we also observe from his appearance in The Siege of Lothal that he also seeks to destroy all elements of his former self.
“I believe he apprentice of Anakin Skywalker lives…” ~ Vader in Siege of Lothal
“Skywalker’s apprentice could lead us to other lost Jedi.” ~ The Emperor in Siege of Lothal
This is a facet to the original trilogy that we never got a sense for. By the time of episode 4, only Kenobi remained as the only remaining element of his former life that he hadn’t destroyed. (This makes us very concerned about the fate of Ahsoka).
But when it came to Luke, Vader showed very different behavior, as we’ve seen in some of the new canon works.
In Issue #6 of the recent Star Wars, we see how Vader learns the true identify of the rebel who destroyed the Death Star (rather hokey too btw):
“I have a son” is how he refers to himself. Not “Skywalker has a son”. With Luke, he remains personally possessive while with others (save for Obiwan Kenobi), he speaks of them as belonging to “Skywalker”.
This continues in Empire and Jedi:
“No, I am your father.” ~ Darth Vader, The Empire Strikes Back
“My son is with them.” ~ Darth Vader, Return of the Jedi
This is a very insightful dialog as it finally gives some context into Darth Vader’s motivation. Whereas his original motivation was to destroy all elements of his past and, serve the Emperor, and become more powerful than all the Jedi, Luke’s presence creates a conflict with these ambitions.
It is really through understanding this can we understand why he didn’t destroy Luke on Bespin and why he ultimately turned on the Emperor. In trying to kill Luke, Vader confronted his true fear – losing his Son.
This really is one of the great elements of these new additions to the Star Wars Saga. They have the power to bring more context that may not have been present in the original trilogy. For what it’s worth, series such as The Clone Wars, Rebels, and even the comic series (of which I have not gotten into much) have really added in a way that I hadn’t expected.