Diavolo/Personality and Relationships

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

- Diavolo, to Polnareff

Diavolo has an aggressive and ruthless personality, highly disliking anyone seeing his true face, and will relentlessly hunt and kill those who do. He is willing to kill his own family and risk civilian lives to prevent his identity being discovered, and attempts to kill his own daughter to stop himself being discovered.

His strong will to overcome his past lead him to creating one of the most powerful organized crime syndicates in Italy, and to keep his position as boss and identity secret Diavolo tortures and murders without mercy or discrimination. As boss of Passione he is highly respected, as Passione is outwardly a just organization dedicated to removing drugs from the streets of Italy. This is, however, all just a front for Diavolo's real plan to make his own drugs (made by Massimo Volpe) 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.

Diavolo is unforgiving of those conspiring against him, probably believing himself to be without fault, and has been shown to treat his subordinates cruelly if suspected of defection. He is even willing to put innocent lives at risk to achieve his goals and secure his identity.

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, often boasting that he is the Emperor and the one chosen by the arrow.

His personality is split so completely that when Silver Chariot Requiem switches everyone's souls, Diavolo and Doppio adopt different bodies: Doppio in Buccellati's body, and Diavolo in Guido Mista's.

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

- Doppio

While Doppio at first appears to be fairly clueless and harmless, he is not unable to look after himself. He has a friendly personality which should not be mistaken for naivety as he proves that he is a lot smarter and more resourceful than he looks. He is faithful to Diavolo and seems to be willing to do anything to help him.

During his fight with Risotto he proves himself to be loyal to Diavolo, almost to the point of stupidity, as he refuses to escape when told so he can find out his enemy's secret and weakness. While at first terrified of what was happening, Doppio uses what resources he has and defeats Risotto with almost no intervention from Diavolo himself.

He is seemingly unaware of their co-inhabitance and appears to consider himself Diavolo's underboss, as Diavolo only contacts him directly. Just before Diavolo takes control, Doppio claims his head hurts and warns people to keep away or stop touching him. After Diavolo has taken care any problems (i.e. killed the person asking about his identity), Doppio regains control once more, entirely oblivious to what transpired, and returns to what he was doing.

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.

While some may ague that Diavolo is the more dominant of the two, it appears that he is merely the more ruthless as Doppio appears to be in control of their body more often than not, taking advice and orders where needed.

Relationships

 * Doppio: Doppio highly respects Diavolo, but only knows him as "Boss", and Diavolo counts on Doppio for various things and even assists him in combat.  He appears to be Diavolo's gopher in most scenarios and the two communicate through Doppio's cell phone or like items in build should Doppio lose his phone, such as frogs and ice cream.  Diavolo even seems to care for Doppio quite a lot, even when most cases it's simple self-preservation (as if Doppio died, so would Diavolo): he attacked the fortune teller who was harrassing Doppio, scared off the taxi driver when he was about to find Diavolo's photo of Donatella, and encouraged Doppio to flee when they were fighting Risotto Nero, as well as later eating multiple frogs in the area in order to restore their iron count.
 * 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 Diavolo did care for Donatella to a large amount and vice versa. He took a picture of Donatella and kept it even after her death, despite being aware of the possibilities of using it against him, and Donatella in return waited for Diavolo to appear again, even as she died.
 * Trish Una: Despite Diavolo frequently trying to cover his tracks, it can be guessed that he at least loved Trish at some point as he not only kept her alive, but had her to begin with. However, once she found out who he was, he attempted to kill her so he couldn't be tracked.

Enemies

 * Giorno Giovanna: Giorno planned to take down Diavolo since the beginning due to his plans to distribute drugs, which were reaching children.
 * 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:
 * 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: In a rejected story line, Fugo was actually a traitor and was strictly loyal to Diavolo.
 * 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.