How do you measure the morality, ethics, and worldview of a person? There are all sorts of theories and measurements out there to evaluate what "good" or "evil" might be, and societal norms are different all around the world. There's no archetypal human being, though the morality chart of Dungeons and Dragons can help a person decide their character's viewpoints.
This is a 3x3 chart with Good, Neutral, and Evil on one axis, and Lawful, Neutral, and Chaotic on the other, making for nine combinations (there is no "neutral neutral", but rather, "true neutral"). That chart is meant for the D&D game, but it can be applied to nearly any work of fiction. Lawful characters are loyal to a cause or an organization, and uphold the rules and regulations of their faction, whether for good or evil. Chaotic characters are impulsive and value freedom and emotion. How might this apply to JoJo's Bizarre Adventure?
9 Lawful good: Jonathan Joestar
Early in the JoJo's Bizarre Adventure series, the two main characters were stark opposites: Jonathan Joestar was a hero and perfect gentleman, and Dio Brando was selfish and wicked (more on him later).
Jonathan will never hesitate to help someone in need. He does it not for fame or reward, but because it's the right thing to do, period. He can't stand criminals or rogues or troublemakers, and his only wish is to rid the world of evil.
8 Neutral good: Jotaro Kujo
Most of the JoJo heroes of the Joestar bloodline are Good on the D&D chart, and Jotaro Kujo, hero of Stardust Crusaders, fills in the Neutral Good slot. He fights to rid the Joestar family of DIO's evil once and for all, and he's determined to save his mother and prevent anyone else from falling victim to DIO's schemes.
But Jotaro a rather reluctant hero too, and he'd rather get on with his ordinary life. The adventure was thrust upon him, and it took him a while to really gain some momentum. He's the type to defeat a villain not to uphold honor and justice, but because that villain is a pain in the butt to live with. Kill the bad guy, get the victims to a hospital, and call it a day. That's the neutral good way!
7 Chaotic good: Joseph Joestar
Now for a rather amusing combination: Chaotic Good! The sly and witty hero of Battle Tendency, Joseph Joestar fights for good and will save the world. But only on his terms, and heaven help anyone who tries to control him or boss him around.
Joseph does things his way and his way only, and he's not above tricking people or even sabotaging him on his quest to vanquish the bad guys. There's no telling what he'll do next, and this trait continues well into Stardust Crusaders, where once again he makes it up as he goes.
6 Lawful neutral: Tomoko Higashikata
In between Good and Evil lies Neutral, and true to the world, this alignment means that these characters would rather just mind their own business. This isn't to say that they're passive, though; they just don't want to evilly scheme world domination or risk their lives to vanquish said evil.
Lawful neutrals, such as Josuke's mother Tomoko, want an orderly and rational life and exist snugly within society. Tomoko, for her part, runs a smooth household, but she'll have no part in Josuke and Jotaro's crazy adventures. She's quick to defend herself, though, if cornered.
5 True neutral: Trish Una
The most neutral combination of all, True Neutral describes someone who is neither a hero nor villain, and they fall in a balance between lawfulness and improvising their life freely. This makes the alignment both broad and difficult to further define, but Trish Una may fall into this category.
Until she helps the gang defeat her father Diavolo, Trish is mainly concerned with keeping her head down and trying to live as an ordinary girl. She wants no part in the crazy plots going on around her, making her a sort of "straight man" (or woman) in Giorno's group. Hey, not everyone relishes the idea of a bizarre adventure!
4 Chaotic neutral: Rohan Kishibe
Chaotic good: they might help you, they might hurt you. These characters seek to fulfill their own goals and interests, and while they are not malicious or wicked, they're also unpredictable, and Lawful Good characters may disapprove. Rohan Kishibe is an independent young man who travels here and there, drawing a popular manga for Shonen Jump.
What's his inspiration? Anything and everything! He's smart, and he can use Heaven's Door to literally read a person's life and use them as source material for manga. He'll beat down anyone who gets in the way of his burning passion for art. He lives alone for a reason!
3 Lawful Evil: Diavolo
And now, we arrive at the three variations of Evil. While it may be tempting to think that all bad guys are the same, evil is as diverse as the other two sects. In the case of Lawful Evil, characters such as Golden Wind's villain Diavolo seek domination and destruction, but in an orderly and intellectual way.
Lawful evil describes someone who enjoys plots and logic, and these characters often orchestrate their plans from the shadows. They think ahead, they devise contingency plans, and they uphold a sense of honor and a code of conduct. Being a mob boss and shadowy mastermind, Diavolo fits this sinister alignment perfectly.
2 Neutral Evil: Yoshikage Kira
A serial killer and stand user from Diamond is Unbreakable, Yoshikage Kira is a fine example of Neutral Evil. These sorts of characters are indeed wicked, and they are willing and able to harm and exploit others to achieve their ends. But neither are they bound to a code of honor, nor are they improvisational or erratic.
They may even live relatively normal lives, like Kira, but they may perform acts and uphold views that would horrify a hero (and break the law). Kira's stated goal is to "live an ordinary life." But what sets him apart from a True Neutral is his penchant for murder!
1 Chaotic Evil: Dio Brando
The list concludes with the most thrilling and terrifying combination of all: Chaotic Evil! These are the bad guys who leave a trail of destruction in their wake. Dio is the frustrated son of an impoverished and cruel man, and at once, he exploits the good favor of the Joestar family to gain power. He poisons Jonathan's dog, harasses Erina, and even gets in fistfights. But he really turns it up to 11 when he first poisons George Joestar, then dons the stone mask and becomes a vampire!
Dio isn't done yet; he sets up a lair in a nearby castle and assembles some minions, bound to no cause or banner but his own, until Jonathan nearly kills him. In Stardust Crusaders, DIO gathers a platoon of stand users to fight for him, and he wants nothing more than to be all-powerful for all time! There's no reasoning with him. The Joestars have no choice but to slay him for all time, and only that can put a stop to Chaotic Evil.