Diavolo/Personality and Relationships

Diavolo
"This is a test... a test from the past that I must overcome."

- Diavolo, to Polnareff

The biggest personality trait Diavolo shows is his paranoia, which is taken to a very dangerous and clinical scale. Diavolo lives most of his life in the shadows with a violent tendency to hunt and kill those who see his face. Agressive and ruthless, something even Passione is aware of, he's willing to kill anyone and even his own family if it means keeping his identity safe - something highly vocalized through his attempts to murder his daughter, who never even met Diavolo herself and only knew things her mother passed down. If he feels as if someone is conspiring against him, they too will become a target, and as seen with Gelato and Sorbet they will be dubbed as traitors if they attempt to find out who he is and thus be made as examples of his wrath.

Because of this paranoia, Diavolo has a strong will to overcome his past, which lead him to creating one of the most powerful organized crime syndicates in Italy. As boss of Passione, he is highly respected (as Passione is outwardly a just organization dedicated to removing drugs from the streets of Italy, even though Diavolo planned to create his own drugs with the help of Massimo Volpe and make them the only product on the market). Buccellati had also initially believed Passione to be doing good, and so felt a great sense of betrayal when this news was revealed to him. However, his subordinates knew of his ruthlessness and carefulness, which extended to such a point that even after Giorno won the trust of Buccellati's group, he still had to wait until they got higher in the ranks before attacking Diavolo.

Diavolo is also unforgiving of those he considers enemies, probably believing himself to be without fault, and in battle is known to brag; he often claims himself a future emperor of the world, the only one fit for the Bow and Arrow, and he justifiably boasts about King Crimson's power regularly. Like other main antagonists in the series, he uses the prefix I or Me (この) to announce his name in a sign of superiority over others.

His second biggest trait is his firm belief in fate. Likely due to being raised by a Christian priest as a child, later on combined with the abilities of Epitaph, Diavolo is very accepting towards the outcomes of fate and realizes that results and outcomes are the only things that matter. Because of this, he is very calm most of the time, taking his time unless danger is immediate. It appears this trait is largely what King Crimson is based off of, as the Stand technically forces the outcome to be the only result, thus literally the only thing that matters.

He seems to knows a lot about how souls work as well, as he understood Buccellati was dead minutes after Doppio encountered him and also knew that the former operative was blind and deaf yet could see and hear Doppio due to precieving his soul. He also knew that Buccellati would see him as Trish if he lent Doppio his "scent", which immediately fooled their enemy. Granted, before he explained this to Doppio, he commented he had no idea how this was happening.

However, unlike villains before him, Diavolo lacks the talents in rationalization and planning. Most of his decisions are very off-the-cuff and rash and throughout Vento Aureo, a large amount of his decisions cost him either time or injuries: for example, instead of allowing Trish to be delivered to him and then killing her when alone, he instead kidnapped her in front of Buccellati and this resulted in a battle between the two. As well, when giving Doppio advice about fighting Risotto Nero, he tells Doppio to either get within 2 meters or flee. He is also persistent in keeping himself a secret even from Doppio, despite the fact that several people have told him that if he and Doppio worked together with equal knowledge they could be unstoppable.

Doppio
"I didn't have to predict that... I guessed correctly... Buccellati won't sacrifice a kid like me..."

- Doppio

In sheer contrasting with his other personality, Doppio is more of a regular kid: harmless, honest, innocent, and while tending to recieve misfortune or harassment, he's not weak and unable to look after himself. Although fiercely loyal to his boss to a point of attempting to fulfil the mission first and foremost, Doppio is smart and quite resourceful, even if Diavolo has to lend a hand here and there. Despite this, though, bits of Diavolo are in Doppio: during the battle with Risotto Nero, Doppio refused to leave the battle or have his boss step in, remaining and doing all he could to find weakness in Metallica. As well, during a few points in the battle, he flat-out argued with Diavolo, despite his more subdued behavior before and after the fight. He also can be violent in his own right, even when Diavolo's eyes are his own, as he was in full control when he nearly tore the eye out of the taxi driver that robbed him.

Even with the bridge of personality to personality, however, he is seemingly unaware of their co-inhabitance and appears to consider himself Diavolo's underboss and, furthermore, an entirely separate person. He does, however, seem to be aware of one thing: whenever he gains a massive headache (a sign of Diavolo about to take control), he warns people to stay away from him. However, the source of this ignorance is unknown; Diavolo was shown moving Doppio out of the ally shortly after killing the fortune teller so he didn't see the corpse, but it's also possible that Diavolo withholds memories and is all-seeing otherwise or that Doppio simply has a poorer memory than his other personality, as demonstrated from Diavolo warning him to either stay away from Nero or get within two meters and then hanging up only for Doppio to immediately forget after a brief headache what he was supposed to do, what he should investigate, and furthermore how he just managed to talk to the boss despite the fact the taxi that just left him had all his belongings (including the broken phone, which even he realized was broken).

Doppio has been shown questioning fortune telling, as he stated that some of the guesses the fortune teller made were simply that due to his appearance ("you're a tourist" because of his bag, "you have a secret" because everyone does, etc.), and he seems good with children here and there as he once successfully borrowed a toy phone from a child while taking a train. He gets angry with people who withhold "phones" from him, but seems ignorant of what the objects really are and seems to blend reality while he converses with the boss. Whenever attacked, automatically Doppio reverts to a state of true fear and submission, often (and truthfully) stating whether he has money or not. He believes himself to be unlucky, which also contrasts with his boss's pure belief in himself.

Interestingly enough, though, Diavolo has made it clear to Doppio that he cares about him. Doppio is usually completely unquestioning, agreeing to whatever his "boss" says. As he dies, Doppio's last thoughts are of his boss. He remains faithful until the end and smiles, saying that if Diavolo is going with them he'll surely win and asks Diavolo to call him, remarking that he feels lonely.

It's theorized that Doppio is the original personality or alternatively the dominate one, as the Diavolo seen in the flashbacks had fashioned his hair into a braid like his future alter ego and Doppio better fits the "honest but dim" description. However, whether this is true or not is unknown.

Relationships

 * With Their Alter Ego:
 * Diavolo to Doppio: Although in most cases it's self-preservation and survival (assuming killing Doppio would kill Diavolo, or vice versa), Diavolo seems to have a lot of affection for Doppio: he put Doppio in a very dangerous position of being the underboss instead of a usual subordinate, he often gave Doppio directions to being successful and even warned him to keep away from Nero and encouraged him to flee, and most peculiar of all, he has a habit of sometimes calling Doppio "[his] (cute) Doppio" with the more down-to-earth "watashi wa" pronoun.  Noticably, when Silver Chariot Requiem activates and Doppio is shot multiple times by Mista, Diavolo almost immediately destroys and impales Narancia on a gate, instantly killing him, and begins to attempt more murders - before it happened, Diavolo was perfectly hidden away and everyone assumed Diavolo was in Buccellati's body.
 * Doppio to Diavolo: While Doppio never learned the truth between themselves, he highly respects Diavolo and always called him "Boss" - though, whether or not Doppio knew Diavolo's name is unknown. Doppio also seems to be Diavolo's gopher, something he takes pride in considering how loyal he was to a point of stubborness, and he seemed heed most of Diavolo's orders when he remembered them.
 * Donatella Una: Although it's unknown how their relationship went, outside of Diavolo using a false name and never talking about himself, it can be infered that it was largely positive. He took a picture of Donatella and she kept it through-out the years despite Diavolo being aware of the possibilities of using it against him. Likewise, Donatella loved Diavolo and told her daughter good things about him (albeit all lies Diavolo said before hand), and it's known that as Donatella died from her illness, she wished to see her lover again.
 * Trish Una: It's infered that Diavolo was never actually aware of Trish's existance until Donatella passed away and La Squadra begun looking for clues on their former employer's identity.  Immediately he put up a plan to kill her and used Buccellati's group as pawns to do so.

Enemies

 * Giorno Giovanna: Giorno planned to take down Diavolo since the beginning due to his plans to distribute drugs, which were reaching children.  Because of this, Diavolo retaliated and made Giorno his enemy.
 * Bruno Buccellati: Prior to meeting Giorno, Buccellati was loyal to Diavolo, even though he was aware of how evil the boss could be. With urging from Giorno, Buccellati became determined to take the boss down as well, eventually dying because of it.
 * Narancia Ghirga: Although not directly interacting with Narancia, he was Diavolo's first victim after Silver Chariot Requiem activated and Doppio was shot by Mista.
 * Leone Abbacchio: Diavolo feared Abbacchio as, due to his powers, he could easily find out who their Boss was. As such, when given the change, Diavolo assassinated Leone while posing not only as Doppio, but also as a simple kid playing soccer.
 * Pannacotta Fugo: Fugo, even with all the evidence given to him, was torn between swearing loyalty to Buccellati or staying on Diavolo's good side.  However he chose to remain on Diavolo's side, and in a rejected storyline Fugo was also sent to kill his former friends.  If the story line was kept, Fugo would have eventually returned to his friends' sides and attacked Diavolo all the same.
 * Guido Mista:
 * La Squadra di Esecuzion: To say La Squadra hated Diavolo is an understatement, seeing how he not only threatened to kill them, but also chopped one of their members up into 36 individual pieces and then mailed each piece individually back to them.  It should be noted that it took La Squadra two years to form a retaliation plan, which Diavolo immediately found out about.