Leone Abbacchio is a somber, quite bitter yet dedicated member of Bucciarati's team.

As a police officer, Abbacchio wanted to keep the streets safe and vowed to give his life in the pursuit of justice. However, the high crime rate among the citizens, their ungratefulness, and the many criminals who bribed their way out of punishment eroded his sense of justice and he began to accept bribes, telling himself that he was still keeping the peace in the city. However, when he failed to properly arrest the same man who bribed him because he feared he would be discovered as a corrupt cop, Abbacchio had to see his partner in the police being fatally shot to save him. Stripped of his rank and moreover openly confronting that he was a criminal like any other, Abbacchio became depressive and eventually joined Passione, only feeling at peace when with the righteous Bruno Bucciarati.

Abbacchio is one of the more serious members of Team Bucciarati. Out of the group, he is one of the most no-nonsense members, taking objectives seriously and allowing very little to entertain him. Among the few times he smiles is out of spite for others (e.g. chuckling at Giorno's seemingly absurd predictions and humorously asking Illuso if he'd lost something after successfully getting Mr. President's key away from him). Abbacchio never participates in the antics of his teammates. However, he still frequently participates in a handful of casual group conversations, especially during lunch. On multiple occasions, Abbacchio would indulge in Mista and Narancia's conversations despite the two's random subject matter, inserting logical responses in-between their tangential nonsense (e.g. talking about what vegetarians would wear or if human flesh tastes good).

During battle, Abbacchio expresses an aggressive side, showing it in frequent verbal threats and insults when talking about and to the enemy.

Abbacchio is highly dedicated to the mission of his group, aiming to absolve himself of or forget his past mistake, and also does so as a way to keep his mind off the memory. Abbacchio is said to have given up on life after the incident that ended his career, only able to give his body as a 'soldier' type in order to further his superiors' goals. In addition, he considers his ability to fulfill a given mission to be a source of honor and pride. As such, he prioritizes the completion of a mission before the life of his allies, and shows a readiness to leave Fugo to his fate. During the fight with Illuso, he easily severs his right hand in order to get Mr.President's key to Giorno, accepting impending death almost immediately before Giorno saves him.

He envies those that are able to pursue justice despite the odds pitted against them and how futile justice appears to be in the face of money. Though Abbacchio admits that he was never able to follow through with his dream, his partner's spirit corrects that he's always kept his moral compass even after becoming a gangster.

When Abbacchio meets Giorno, he presents the new member with a teacup of his own urine as a bullying tactic. During their time together, Abbacchio never ceases to confront Giorno and express his contempt for the new member. Not only does he remain highly critical of Giorno's every action and word, he also refuses to show Moody Blues in action in front of him, not trusting Giorno in the least with the secret of his Stand. Somewhat prideful, Abbacchio promises to beat Giorno up after the younger member consistently proves his own course of actions optimal whenever their opinions differ. But, although he despises Giorno and manhandles him from time to time, he never goes as far as hitting him. Despite himself, Abbacchio is impressed by Giorno's actions. For his part, Giorno respects Abbacchio as a senior member of the team.

When Abbacchio visits Pompeii, he shows a former great interest in the ruins as he mentions that as a child, he used to walk all the way there from Naple