The title itself — How to Get Away With Murder — is a clear sign that the events in the show occur in a moral gray area. Professor Keating's acclaimed series of lectures on navigating the pitfalls associated with homicide cases is where everything begins (and ends.)
There are a number of murders that take place, but the reasons behind each of them are not always fathomable. The characters are usually trying to protect themselves, or their loved ones, but their actions only get worse and worse as they are pulled into the deep end. The list below analyzes the ethical motivations of the main characters, using the Dungeons & Dragons moral alignment system.
Annalise Keating - Lawful Good (Crusader)
The whole world is out to get Annalise, from her disloyal students to political superpowers. Considering all the hate directed towards her, it is always surprising when one realizes that she has committed exactly zero murders. Instead, she plays the Crusader, saving her friends and family from the crimes they get themselves involved in.
She might be brusque, impatient, and rude, but that does not mean she is anything less than the most compassionate soul in Philadelphia. As her mother explains in the final season, Annalise's empathy derives from overcompensating for her own "motherless" childhood by protecting literally everyone else.
Bonnie Winterbottom - Neutral Good (Benefactor)
Under the spiritual (?) guidance of Annalise, Bonnie learns how to (at least partially) overcome her trauma; no thanks to Sam's psychological meddling. She is a true Benefactor — although she has often been shown trying to convince Frank and Annalise to give up on the students, she takes incredibly deep plunges for the people she cares about.
For instance, upon seeing the bloodied state that DA Miller is in, she coldly proceeds to murder the man she once loved in order to protect Nate Lahey from being punished for this crime.
Nate Lahey - Chaotic Good (Rebel)
Although he starts off so upright that he might well be called morally rigid, Nate's unfortunate encounters with Annalise and her students alter his personality. He later opts to take the law into his own hands, for instance, when he kills Laurel's brother, Xavier Castillo (out of pure spite, as he has already obtained the information he wants)
Given the Castillo's illicit dealings and their murder of Wes, Nate's action classifies him as a Rebel. Fortunately, everything ends well for him: he is depicted as a philanthropist who builds homes for the innocent victims of the law.
Laurel Castillo - Lawful Neutral (Judge)
Laurel is largely impartial to the mess that Michaela, Connor, and Asher constantly produce, with the exception of Wes. Nevertheless, her Judge personality allows her to view the situation with as little bias as possible and is probably the only reason that Wes even gets as far as he does in his Lila/Rebecca quest.
More importantly, Laurel's love towards her friends might be deep, but her decision to go into hiding only take into account the guardianship of her baby, Christopher Castillo. Her self-preservation is regularly mistaken for betrayal, but she doesn't let that stop her, anyway.
Ophelia Harkness - True Neutral (Undecided)
Ophelia, the wise matriarch of the Harkness family, is a classic example of the Undecided category. This is not because she doesn't care about anyone; quite the opposite, in fact. Coming from a broken home, raising two daughters all by herself, working a variety of jobs to give them a better life, having to deal with predatory relatives: all these experiences have given Ophelia a sense of intuition and inner strength that even Annalise lacks.
She prefers to murder her brother-in-law in order to safeguard her daughters, but she only does this because there was no other alternative for poor, black women in 1960s Tennessee.
Tegan Price - Chaotic Neutral (Free Spirit)
Tegan Price is a law prodigy, probably only surpassed by the woman of her dreams. She embodies the Free Spirit, and not always in a good way. For instance, she continues to hound her ex-wife even after being explicitly told not to.
In the case of Annalise Keating, Tegan finds herself inexorably drawn towards the older woman, at one point blurting out that she has feelings for her. The consequences of her confession may have seemed bitter at first, but the final montage of Annalise's life shows that she took Tegan up on her offer.
Michaela Pratt - Lawful Evil (Dominator)
Initially, Michaela Pratt spoke, thought, acted, and even dressed like the legal powerhouse she used to dream of becoming. Over time, however, her involvement in Sam Keating's inevitable murder has frayed her psyche, resulting in bouts of paranoia and reckless decisions.
She behaves as a Dominator, not only towards her classmates or Asher but also Annalise — a prime scenario being her affair with Caleb Hapstall, one of her mentor's clients, which almost destroyed their entire case. Michaela is the only one of the Keating Five who refuses to atone for her ambitions, but this results in the destruction of her friendships.
Frank Delfino - Lawful Evil (Dominator)
The wayward Keating child, Frank Delfino cannot be fully blamed for many of his horrible deeds (several of them are performed under Sam's threat or for Annalise's benefit.)
Nonetheless, the Dominator within him emerges far too often, and almost always gets his way, regardless of how much the two women in his life plead for him to withdraw from the situation. Frank occasionally inflicts his power on Annalise's interns and has been known to sleep with a number of them. At least until Laurel comes into the picture.
Governor Birkhead - Neutral Evil (Malefactor)
Being a Malefactor, Lynne Birkhead would rather preserve the status of her office than let an innocent man get out of jail alive. She becomes the antagonist of the show the minute she manipulates the system to have Nate Lahey, Sr. shot and killed "in a prisoner altercation."
Her determination to crush the only person strong enough to be a threat to her would have been admirable, if only she had gone about it like a decent human being. But no, Governor Birkhead relies on her complex network of lies and deception to ensure political victory.
Sam Keating - Chaotic Evil (Destroyer)
One of the final episodes of the series, "What if Sam Wasn't the Bad Guy This Whole Time?", prods at the notion that the world's worst psychologist may, perhaps, be forgiven for all the terrible things that he has done.
It doesn't matter, because Sam Keating is a bad guy, irrespective of his childhood misery. He is an undeniable destroyer: of moods, of hearts, and of lives. What's worse is that he hates having to get his hands dirty, so he forces his own son, Frank, to murder his pregnant teen lover.