Dio Brando/Personality and Relationships

Personality
Dio is consistently manipulative and violently domineering, and has repeatedly shown a lack of conscience and empathy.

Dio's most recognizable characteristics are his boundless ambition and his love of power. Abused by his father and having lived in the most miserable living conditions, Dio set for himself the goal of becoming the richest, then the most powerful being on earth. To do so, Dio used anything or anyone that he could use to further his goals, disregarding any kind of morality who would restrain the range of actions available to him. Using either manipulation and seduction, or plain violence, Dio constantly sought to become more and more powerful. Dio enjoys being in a position of power and has repeatedly stated how great he felt being in a dominating position. On the contrary, Dio never tolerated that someone could stand up to him or equal him in power, and was several times enraged and deeply disturbed at the thought.

Throughout his life, Dio has tended to surround himself with witless cronies and later minions, who were attracted by his natural charisma. Not thinking much of them at first, he then selected those he deemed as particularly evil, claiming that an evil person wasn't bound by rules such as honor and thus were stronger mentally. This belief culminated in including the absorption of 36 souls of sinners, or as he claims particularly strong souls, to unlock a power greater than that of The World.

Naturally, Dio is an incredibly selfish person, only looking over his own interest and overlooking those of others at best, trampling them on the ground at worst. Araki personally considers Dio to be technically bisexual. He remarked that Dio can and will openly offer himself to either sex using any method, as long as the person suits his present desires. Since he is selfishly interested in their capabilities, however, Araki commented that Dio is the type who is incapable of loving another person wholeheartedly. The only persons he can be said to have loved was his mother, Jonathan Joestar and Enrico Pucci, Dio recognizing Jonathan's worth as equal to his own, and having been friends with Pucci. Still Dio stole the former's body and his friendship was nonetheless merely a part of a grander plan to further himself.

For unknown reason, Dio let several women who met him live and bear his children.

Phantom Blood
"I reject my humanity! JoJo!"

- Chapter 11, to Jonathan, before wearing the Stone Mask

In Phantom Blood, Dio is ambitious, arrogant, and megalomaniacal, seemingly able to do anything to achieve his aims. His natural ruthlessness is exposed very early when he swears on his father's grave to exploit the Joestar family despite them being kind enough to adopt them. In order to place himself in a better position to replace Jonathan Joestar and obtain the Joestar family fortune, Dio used the most underhanded means to break him mentally. These methods included: humiliating Jonathan in public sport fighting, ostracizing him from his friends, and finally stealing Erina's first kiss to drive a wedge in their budding relationship. When he is eventually foiled, Dio opted to slowly poison George Joestar I and kill Jonathan with the Stone Mask to make both deaths seem natural and accidental. Dio has shown a remarkable determination to reach his goal, never losing his drive despite the numerous defeats he suffers throughout Phantom Blood and always tried to find a way to get back at Jonathan for them.

Dio's lack of empathy is also apparent, since despite having lived for years with the kind Joestars, he never thought of them as anything more than obstacles, and is hinted to utterly resent the upper class he frequents. Dio has been maintaining a facade of a charming and agreeable person to everyone save Jonathan, yet never came close to anyone. At the end of the part, the only person Dio appreciated was Jonathan Joestar, begrudgingly acknowledging his valor as his archenemy and "granting" him a painless death, and was even shocked to see him die. Dio also sadistically changed a mother into a zombie just to watch her devour her baby. Overjoyed to have changed into a powerful vampire, Dio spent his battles taunting various humans about their weakness and belittling them in favor of the apex predator vampires.

Dio shows a lack of restraint in his violence, and is prone to murderous outbursts even as far as his childhood, notably trying to stab Jonathan when he beat him up, and violently slapping Erina. He was also incredibly mean to Jonathan's dog, Danny, going as far as kicking him on their first meeting. When Dio was defeated by Jonathan, Dio incinerated the dog. Dio is shown to be utterly enraged when someone stands up to him, which is the cause for his outbursts.

Dio's personality could be explained by his poor childhood and the abusive relationship he shared with his father, Dario Brando. Speedwagon, however, denied this as a cause for Dio's personality, claiming that Dio was simply born this way, and that poverty had nothing to do with it. True to that, Dio was already an immoral person but then openly relinquishes his humanity in favor of becoming a vampire upon being cornered by the police. He trades his underhanded scheming persona for a more arrogant, hedonistic, and dismissive of humanity personality that revels in his evil. Nonetheless, Dio respects determination and said that much to Jonathan that his determination was equal to his own, earning him the dubious honor of serving as Dio's new host, as Dio was reduced by Jonathan to a head.

Dio's potential for empathy is emphasized in both the manga and the anime, when Dio is shown to have killed his own father out of revenge for the abuse against his mother, rather than as a step in his scheme to rise in society.

Stardust Crusaders
"Everyone survives in pursuit of peace of mind. ... Aren't you uneasy, preparing to fight me, knowing you may die? ... If you join me, I will give you peace of mind that will last forever."

- Dio to Polnareff, Chapter 248

Reappearing in Stardust Crusaders, Dio ultimately didn't change much since his burial at the bottom of the ocean, still being his megalomaniac and murderous self, but nonetheless having matured a little by recognizing valor in others and being more calm.

Dio doesn't appear much in Stardust Crusaders, but is seen discussing various philosophies with Stand users he wishes to recruit, and with his already loyal followers, particularly Enya who serves as his main advisor. It seems equally likely that Dio does this to manipulate and persuade as that he believes what he says, but nonetheless acknowledges the power and valor simple humans can have, notably respecting one's willingness to die for his goal. Wishing to quickly dispose of the Joestars, he listened to Enya who told she already sent agents to deal with them, and quietly rested in his mansion to gain more strength. Furthermore, Dio learned his lesson and stops to underestimate his opponents, being particularly careful around the Joestar bloodline. He nonetheless sneered at other Stand User's efforts to fight him, notably Kakyoin's, whose discovery ended up being crucial in his defeat.

This time, Dio is far more calm and collected. Maybe knowing that his Stand The World is far above anyone's reach, Dio is more tolerant of people resisting him, and didn't react to Polnareff's taunts. Dio even seems to appreciate Hol Horse's insubordination, which confirms the mercenary's strength, and let him go try to assassinate Jotaro. However, Dio is still callous about human life and killed anyone who would fail him, even Enya - who was his closest advisor - and Daniel D'Arby when he couldn't handle the pressure of possibly revealing Dio's secret to Jotaro. True to himself, Dio is enjoying the fact that he is wielding the most powerful Stand in his organization, being unconcerned by the heroes' effort to discover his power as he thinks they are meaningless. When Jotaro reveals himself to be able to move within the stopped time, Dio is very distraught but recomposes himself quickly, devising other plans to get rid of Jotaro by exploiting his advantage. The full scale of his insanity is visible when, overjoyed to have compleely fused with Jonathan's body and being at full power, Dio declares that "the greatest high" and drills his index finger into his skull. His final speech exposes that he still is willing to use any way to win and despises any concept of honor or revenge, ultimately using a cheap trick to blind Jotaro momentarily.

Stone Ocean
"...Beyond the powers of my Stand is where you need to go in order to find Heaven. What you need is a trustworthy friend ... Will I, DIO, be able to meet someone like this one day?"

- Dio's Diary

In flashbacks placed before the events of Part III, Dio demonstrates a burgeoning ability to be genuinely nice to another person in numerous conversations with Enrico Pucci. Intrigued by Pucci, who let him be despite suspiciously hiding in a church, Dio healed his crooked foot, a genuinely nice gesture, and gave him an Arrowhead, which would grant him Whitesnake. During these flashbacks, we see Dio peacefully chatting about random trivia, and confessing to Pucci that the priest could make him be at peace. Once daring Pucci to steal his Stand, to Pucci's refusal, Dio thanked him for his fidelity, and admitted that he feared that Pucci would betray him.

Is it debatable how good a friend Dio truly was, notably considering Pucci's good nature during his youth as opposed to his later evilness. Also, Dio seems to have built that friendship to further his ambitions, which questions how sincere it was. It is implied that Dio wanted to use his Stand to create a perfect world for himself and a handful of subordinates. He enlisted Pucci as his living "conscience", in case he would go crazy and veer "off track".

Family

 * Dario Brando: Dio hated his father and saw Dario only as a stepping stone in his path to ascend in society. In both the manga and the anime, Dio's hatred stems from the abuse Dario dealt Dio's mother with his alcoholism, as well as Dio himself. He emphasizes this by spitting on his father's grave before leaving for the Joestar mansion.
 * Dio's mother: Though she isn't seen interacting with him, it's very clear that Dio loved his mother deeply, and the abuse she was dealt by his father was one of the reasons Dio slowly and painfully killed Dario.
 * Giorno Giovanna: Dio is not shown to have interacted with Giorno, although Giorno keeps a photo of his father in his wallet. However, it is unknown where he got it from or if he knows Dio is his father. Also of note is that while Dio was shown to have sucked the blood out of young women, killing them in the process, he had neglected to kill Giorno's mother because he felt she was abusive, as revealed in Over Heaven.
 * Ungalo, Donatello Versus, and Rykiel: Similar to Giorno's case, the mothers of all three men were left alive. However, none of them inherited Jonathan's spirit. All three know their true father only after their fated encounter with Pucci.

Allies

 * Enrico Pucci - Dio's encounter with Pucci is presumably the most prominent example of humanity displayed by him and was his first proper friendship with another person, as he showed compassion by healing Pucci's foot when they first met. Through the time he spends with Pucci, Dio comes to trust him enough to take control of his plan and at one point, Dio forced Pucci's hand into his head and nearly had his Stand Disc removed to test Pucci's loyalty to him.
 * Vanilla Ice - While the former is fanatically loyal to his cause, even willing to chop off his head to prove his worth, Dio notes that Vanilla Ice often forgets about the doors while he uses his stand Cream to put a hole in the wall.
 * Wang Chan - While at first a provider of his secret oriental poison, after becoming a vampire, Dio used him as a scout and aide once his head is chopped off. Despite his dependence on him, he doesn't take his insults to Jonathan lightly and threatens him for it.

Enemies

 * Jonathan Joestar - One of the most impactful relationships Dio ever had was with his adoptive brother, Jonathan Joestar. He initially viewed his adoptive brother as a stepping stone and pest to be driven to despair and abused in order to gain the Joestar family fortune. After being beaten once, he viewed him as more of a threat, feigning brotherly bonds in public, while secretly poisoning George Joestar in order to get his fortune quicker. He intended to kill Jonathan with the Stone Mask, but upon discovering the hidden power to unlock the vampire powers of man, he decided to use it on himself in order to become one. After another failed attempt to kill his adopted brother, due to his ego Dio decides to have others face him rather than turn Jonathan into a zombie himself. After being bested by Jonathan, he quickly changes his mind, only to be thwarted again. In their final confrontation, he admits he respects Jonathan (to the point of scolding Wang Chan for scorning him) and is genuinely shocked when Jonathan dies.
 * William Anthonio Zeppeli - Due to Dio having used the Stone Mask and becoming a Vampire, Zeppeli immediately viewed Dio as an enemy once he learnt about the incident at the Joestar Mansion and due to his own father using the same mask to become a Vampire himself. Dio himself is dismissive of Zepelli's hatred towards his vampiric ways and connection to the Stone Mask.
 * Robert E. O. Speedwagon - After hearing from Jonathan what Dio was doing to George Joestar I, Speedwagon decided to help with finding the man that sold Dio the poison. After everything that had happened at the Joestar Mansion, he went along with Jonathan and Zeppeli to defeat Dio, knowing that he was too dangerous now as a vampire to be left running around.
 * Dire, Straizo, and Tonpetty - Being Hamon Warriors, the three knew the dangers of the Stone Mask and viewed Dio as an enemy because of his use of the Stone Mask. Out of the three of them, Dire was the one who really wanted to defeat Dio on his own, due to Dire having been a friend of Zeppeli's for many years and Dio having a role in his death. At the time, Straizo knew that defeating Dio was important; however, years later, he would admit to the older Speedwagon that he was envious of Dio due to the fact he would never age while Straizo would. This envy became so much that he would later use the Stone Mask on himself just so he could become young again.
 * Joseph Joestar - Dio needed Joseph in order to complete the merger of his head with Jonathan's body, secretly manipulating his minions to bring him closer and closer in order to drain his blood. Joseph had heard stories of Dio from Erina when he was small and knew of the danger he would bring. His hatred for Dio intensified, however, when he learnt that Dio had stolen the body of his grandfather, Jonathan Joestar, to use as his own. This hatred got to the breaking point when Dio's very existence threatened the life of Joseph's daughter Holy Kujo. Figuring out that since Dio was the cause of all the Stands in the Joestar family activating, it was more than likely that killing him would save Holy, so Joseph, along with his grandson Jotaro, his old friend Mohammed Avdol, and new ally Noriaki Kakyoin, decide to go to Egypt where Dio had gone to hide, and kill him.
 * Noriaki Kakyoin - Having met Dio when on holiday in Egypt with his family and then put under his control with a Flesh Bud, Kakyoin was loyal to Dio and would do anything he wanted. But upon having the bud removed by Jotaro and seeing the harm Dio was causing on Holy Kujo, who had shown him kindness as he was recovering at the Kujo residence, Kakyoin decided to go with Joseph, Jotaro, and Avdol to Egypt to defeat Dio.
 * Jean Pierre Polnareff - Like Kakyoin, he too met Dio, who then placed him under his control. After having the Flesh Bud removed by Jotaro, Polnareff decided to join the team, though at first for his own goals, as Polnareff theorized that Dio would know where his sister's killer would be. Even after he avenged her sister's death Polnareff chose to stay with the group to defeat Dio. After the deaths of both Avdol and Iggy, Polnareff vowed to defeat Dio no matter what.
 * Mohammed Avdol - Unlike Kakyoin and Polnareff, Avdol knew who Dio was immediately upon meeting him, due to having heard about him from Joseph; as such, he knew he was an enemy right off the bat and managed to escape from him before he could be put under his control. With Dio threatening Holy's life due to him activating all the Stands in the Joestar bloodline, Avdol, along with Jotaro, Joseph, and Kakyoin decided to journey to Egypt to defeat Dio.
 * Iggy - Iggy was dragged against his will into joining the Joestar Group in Egypt, and as such didn't care about Dio or what was happening, being more concerned about himself. After his fight with Pet Shop though he decided to help the group defeat Dio, as it was because of him Iggy was brought to Egypt in the first place. Dio and Iggy never encounter one another though, as Iggy dies protecting Polnareff against his fight with Vanilla Ice, one of Dio's servants.
 * Jotaro Kujo - Dio viewed Jotaro as much of a threat as Jonathan was, if not more, going to extremes to outwit and make sure of his death. While Jonathan was an opponent Dio respected, Jotaro was an opponent Dio feared. Jotaro, on the other hand, despite being able to hide his emotions from other people, was secretly worried about his mother's failing health caused by her Stand and wanted to defeat Dio as quickly as possible, as her Stand was caused by Dio activating all the Stands in the Joestar bloodline at the same time. After Dio had apparently killed Joseph right in front of him, Jotaro's hatred for Dio intensified, and after a long and grueling fight with the vampire, Jotaro finally managed to kill Dio.