Boss of an Italian gangster organization "Passion", secretly controlling all underground businesses and factories in Italy. The influences of Passion spread across fields including dope slanging, trades, and politics.
Borns inside the jail after his mother's two-year pregnancy, Diavolo gains naturally grew strange pink hair, his eyes also stay wide open after his birth. Those strange things happen to him and his weird appearance makes him looks like an avatar of the devil.
Diavolo is evil incarnate, he lived a happy childhood after been adopted by a godfather and seems like a cowardly child for a long time. However, one day the godfather accidentally finds Diavolo's mother buried under floors inside his house. Diavolo then kills the godfather, sets fire, and burns the whole village, and he lefts his home. Nothing in his life experiences forges his evil, he just borns to be that way.
After getting a job digging an Egypt remnant, Diavolo accidentally finds six Stand Arrows. Those arrows can awake beings generated from people's life energy and represents people's mind and spirit, those beings are "Stands". He sells five arrows to Dio Brando's followers and gains a lot of money. Utilizing that money, Diavolo creates the "Passion", and he secretly runs the organization.
Another secret of Diavolo is that he has dissociative identity disorder. There is a secondary personality named "Doppio" hides in his body. Doppio is a cowardly person who seems harmless. Diavolo usually lets Doppio controls his body and sets an identity for Doppio as Diavolo's trustful follower. Doppio displaces clearly mental disorder, he always uses a phone to speak with Diavolo, without noticing Diavolo is actually another personality speaking to him inside his head. When he cannot find a phone immediately, he will grab a random object near him as an imaginary phone. Diavolo usually lets Doppio as his messenger to spread his commands, since no one in the organization actually saw Diavolo, everyone just believes Diavolo has never shown up. This personality switch is also abnormal since Doppio seems short and skinny, but when Diavolo takes control, his body somehow gets stronger with muscles pops out and his eyes turn into a strange shape. When Doppio takes control, Diavolo usually ties up his hair.
Diavolo also stabs him with the remaining arrow, and awakes a Stand named "King Crimson". He gains the power to delete time for several seconds.
After discovering he accidentally left a daughter Trish Una, he commands a guardian team composed of Stand users to bring Trish to his base in order to kill Trish on himself.
However, a member of the guardian team Bruno Bucciarati finds out Diavolo's true purpose and decides to betray him and protect Trish. Although Diavolo kills Bucciarati with one shot, another team member Giorno Giovanna using his power turns Bucciarati into an undead body. Then, the whole team turns against Diavolo except one decides to quit and left.
Diavolo finds out Stand Arrows he found can awake people's Stands, which are entities generated from people's life energy representing people's mind and spirit, each stand has a unique superpower, and people who have abilities to summon stands were called "Stand Users". Diavolo's stand is named King Crimson, it appears like a strong, muscular man with red, leather-like skin and white armors covering shoulders and belly. It has strange eyes like octopus's, and a small, pink face attaching to its forehead.
As a Stand User, Diavolo can summon King Crimson whenever he wants or hides it in his body. King Crimson is a close-range Stand, so it stays about 2 meters from Diavolo's body after being summoned and seems always floating above the ground. The power of King Crimson is to delete time for several seconds.
A secondary power of King Crimson is Epitaph, which triggers by the small face on the forehead. This power is to predict several seconds of the future to Diavolo.
- Delete time: King Crimson can somehow delete time for several seconds. When this power triggers, people will do what they intend to do during this time, and forget these several seconds. This is because time is deleted during those several seconds, so normal people won't experience this time, they also cannot change their decided moves during this time. Only Diavolo himself senses the deleting time and ables to move freely during these seconds. From other people's eyesight, it seems Diavolo just suddenly disappears.
- Intangible: When deleting time, Diavolo becomes invisible and intangible in the few seconds he deleted. This power makes him able to avoid attacks effectively. However, this intangibility also makes him unable to interact with other objects when deleting time. Diavolo cannot touch or attack other people when deleting time.
- Predict Future: The little face on King Crimson's head can trigger a power named "Epitaph". This power will show visions of several seconds of the future to Diavolo's eyesight. This power is extremely practical when co-works with the power of deleting time. Diavolo can sense possible attacks by Epitaph, and deleting time to avoid those attacks by becoming intangible.
- Strength: King Crimson has superior strength among most Stands. Its strength is rated A by Stand's standard, and it can break rocks, walls, and flesh bodies. The signature move of Diavolo is to penetrate opponent's body with King Crimson's fist. Diavolo usually deletes time and then sneak behind his enemy, then suddenly attacks his enemy after the time flows normally.
Diavolo desires to be a secret underground emperor. He doesn't let anyone know his true identity and never shows up himself. To avoid exposing his identity, he even decides to kill his only daughter in order to prevent anyone from investigating his identity through his bloodline.
His Stand power is almost invincible in solo fights since he can predict and avoid all attacks by deleting time, but he tends to avoid fights when facing multiple opponents since he can't bear the risk of left any enemy sneak away and reveal his identity.