Wait, one of the quintessential big-screen villains is not normal? Oh perish the thought.
That said, I know a bit about Borderline Personality Disorder having been (incorrectly) diagnosed with it at one point, despite having some of those traits (I've grappled with emotional problems my entire life). Anyone who says this is really pushing trying to make a point.
One thing to understand about a Borderline personality is that your dealing with a true sociopath. While there are traits common to borderline personality that can identify it, there are also traits that can be present which will instantly disprove it.
In the case of Anakin/Vader, consider that one of the key points of the character is his love for Amidala, it's that relationship, the forced secrecy, and similar things that were insturmental to his fall to the dark side. Even after the fact he loves his own son, offering to betray the emperor for him, and ultimatly redeeming himself when he casts down The Emperor at the end of Return Of The Jedi.
A Borderline personality is by definition totally self interested, his concern for others, which motivates a *LOT* of what he does (no matter how badly written) even the betrayal of the Jedi, means that he could not be a true sociopath, or borderline personality, unless one was to say he was faking most of his relationships through the storylne (which Borderline personalities do), this is however unlikely since he didn't have anything to gain in most cases by doing so. In fact, his personal interests would have been better served at the end of "Return Of The Jedi" had he like Luke fall.
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One other point to understand is that there are other forces at work here which are not understood to exist by science. We're dealing with prophecies, and cosmic manupulation. The Star Wars universe works in cycles where good and evil both take turns "ruling" creation, with a period of balance in between. "Star Wars" is about the transition from a time period of good, to a period of balance, which will end in an age of darkness (a bit of a downer). When it comes to Anakin "The Force" has basically decreed that he is going to be the one to "bring balance", a point which is misunderstood, since with the good guys in control the only place for them to go is down. In "Star Wars" the universe is literally conspiring to make certain things happen, and Anakin is being manipulated. A lot of the coincidences inherant in the storyline are not supposed to be coincidences in a literal sense but the mechinitions of The Force.
This is integral to "Knights Of The Old Republic II" (which George Lucas was involved in the writing of apparently) where while the narrative falls apart towards the end, the primary motivation of the "bad guy" is to destroy "The Force" itself, put an end to universal cycles, and give people true free will and control over their destinies. How the coup de grace was intended to be delivered was never revealed, but that was what it was all about, and it kind of spelled out how a lot of things worked, and why we had prophecies, and you had great fluctuation in the power of Jedi and Sith comparitively... it depended on what side The Force decided was supposed to be ascendant at any given time.
As this affects this, one has to understand that Anakin's personality flaws come from a reality where he is being manipulated, and to some extent realizes he cannot do, or have, what he wants... at all. He is more or less fighting against a universe that wants to turn him evil, but then things happen (like seeing his mother killed) specifically to drive him into rages so he will fall to The Dark Side.
As far as we know in reality, and as science allows for, there are no exterior, cosmic forces, literally manipulating people and their enviroment towards given ends. Granted nobody (except arguably Kreia, and at the end "the Last Jedi", as well as us players/readers/watchers) knows about this, it's still an overall factor. Outside manipulation of events is involved.
This means that any kind of diagnosis based on real world science, involving a fantasy character who is a "chosen one" manipulated by fate, cannot be done with any accuracy.
Going past the acting and portrayal of the character, Anakin is basically supposed to be a nice guy, gone emo, due to the fact that everything involving him in some way goes to utter cr@p, because the universe wants him to bring down the current domination of good guys.
In some respects, Anakin is similar to Michael Moorcock's "Elric" (though not directly), as both basically dealt with the same theme of higher powers demanding the protaganist drag their world into an age of evil/chaos, and them deciding to try and resist this fate. In the end Anakin more or less does what he is supposed to (he brings balance, it wasn't time for evil to actually take over, hence the death of Papaltine), in Elric he pretty much hits a giant "reset" button and leaves everything like it was before, enraging his manipulators when he blows the final form, and getting run through by his own blade in punishment.
