I am in no way actually qualified to do this but today I shall be diagnosing Anakin Skywalker with BPD (Bordeline Personality Disorder) and explaining why I'm right.
My "qualifications" are: my own former diagnosis of bpd and having taken A-level psychology.
The DSM-5 describes BPD as a pattern of instability in interpersonal relationships, self-image, and emotions, as well as impulsivity beginning by early adulthood. In order to be diagnosed the person must present at minimum 5 of the 9 following bpd criteria:
1. Frantic efforts to avoid real or imagined abandonment
This one is pretty obvious as Anakin literally fell to the dark side, let all other jedi be killed, and ignored Palpatine being the major sith they were spent years searching for and fighting, in order to gain the knowledge he thought he needed to keep Padmé from dying. Additionally, on Mustafar when he spots Obi-Wan on Padmé's ship he goes to far as to strangle her as he views this as abandonment and betrayal from her.
2. A pattern of unstable and intense interpersonal relationships characterised by alternating between extremes of idealisation and devaluation.
This one is very obvious in his relationship with Obi-Wan. Going from caring about him- "I'm not leaving without you, Master" (ROTS) and saving his life at minimum 9 separate times throughout the clone wars, to hating him- "I HATE YOU" (ROTS), "YOU TURNED HER AGAINST ME" (ROTS), "it's all Obi-Wan's fault! He's jealous!" (AOTC), just to name a few examples.
3. Identity disturbance: markedly and persistently unstable self-image or sense of self.
The entire plot point of Anakin separating his identity from that of Darth Vader and his own. Later, when Darth Vader takes complete control he refers to his past self as only "The Jedi", showing a complete split of identity and self. Furthermore, throughout Attack of the Clones there are multiple instances of Anakin believing that he is the most powerful jedi ever and that he is invincible and yet he was unable to save his mother, this shows cases of an unstable sense of self wherein he switches between idolising himself and not living up to that idolisation.
4. Impulsivity in at least two areas that are potentially self-damaging (e.g. spending, sex, substance abuse, reckless driving, binge eating).
The first area to prove this is his podracing which then later on influences how he drives. Anakin was podracing since he was a young child (Phantom Menace), which can be excused as he had no other choice while he was a slave and then did it to gain his own freedom, however, throughout the earlier books of Obi-Wan's and Anakins adventures, Anakin continued to sneak out of the jedi temple to bet on and occasionally participate in podracing on the lower levels. Podracing is an incredibly dangerous sport with an incredibly high death rate. Later on we can see how Anakin continues to drive recklessly, very often crashing his vehicles.
Now, he doesn't canonically meet any of the other suggested areas, however, I would like to raise his impulsivity throughout the Clone Wars. Yes, they were at war, however, Anakin put his life at risk unnecessarily on many repeated occasions, barely coming out unscratched.
5. Recurrent suicidal behaviour, gestures or threats, or self-mutilating behaviour.
Now, this is a controversial one but I think that Anakin does in fact meet this criteria as well. Firstly, continuously putting his life at risk unnecessarily throughout the clone wars can be seen as suicidal behaviour, yes he's not actually attempting but he is not not attempting, if that makes sense. Secondly, on Mustafar when Anakin jumped despite how Obi-Wan was positioned, it was obvious that Anakin was not going to win that, however, he attempted to anyway, very nearly costing him his life. Thirdly, later as Darth Vader when he is told that Padmé is dead there are multiple occurrences throughout the comics where he wishes for death rather than to continue living without his Padmé. Lastly, he sacrifices himself The Return of the Jedi in order to save Luke and beat Palpatine.
6. Affective instability due to marked reactivity of mood (e.g. intense episodic dysphoria, irritability or anxiety usually lasting a few hours or a couple of days).
Anakin becomes very easily irritated about nearly everything, such as sand or the Jedi's lack of faith in him. Throughout ROTS he becomes exceedingly frustrated with both the Jedi council and Obi-Wan believing that they do not trust him and are purposely settling him up for failure. He is increasingly anxious about Padmé and his child's deaths based on a nightmare he had, going as far as to turn to Palpatine for help and turning to the dark side to save them. He is also portrayed throughout the Clone War's as struggling with mood swings, such as when he force chokes Clovis.
7. Inappropriate, intense anger or difficulty controlling anger.
He massacred the Tusken Raiders, including the innocent ones, for the murder of his mother. He wiped out all the Jedi at the jedi temple at the command of Palpatine. He force choked Clovis (and multiple other characters throughout the Clone War's) after finding him hitting on his wife. He tried to kill Obi-Wan believing that he had turned Padmé against him.
8. Chronic feelings of emptiness
This one is the only criteria I am struggling to pin on Anakin. He does not seem to portray feelings of emptiness, rather the opposite, as he struggles with his feelings of anger, distrust, attachment, love and heartbreak. However, one could argue that as Darth Vader, he does portray this quite often as he is often depicted throughout the comics as struggling to feel much of anything.
9. Transient, stress-related paranoid ideation or severe dissociative symptoms.
Many people argue that this is the one that Anakin does not meet, however, I would strongly disagree. In the deleted scenes of ROTS and in the books Anakin is shown to be paranoid about Padmé and Obi-Wan's relationship, going as far as to even accuse Padmé of cheating on him with Obi-Wan. This is further shown when Anakin spots Obi-Wan on Padmé's ship and believes that he has turned her against him. He also shows paranoia regarding Padmé and his mother's deaths based on dreams he has had. Further, he believes that the Jedi do not trust him and are turning against him.
Those are all 9 criteria of BPD. As I said before one must meet at minimum 5 for a diagnosis of BPD and as I have shown here Anakin meets nearly all of them, if not all, and so it is in my (correct) belief that Anakin Skywalker portrays BPD and life with it exceedingly well, and is actually a really good and accurate representation of it (even though it's not actually canon).