The Boys offers plenty of unique and remarkable characters, each one with their inimitable personality and characterization (outfits, superpower, backstory, moral alignment). However, one of the pivotal traits that characterize each protagonist (or antagonist) is their moral values, their ethics. With that usually comes a backstory and the motivation of their actions and plot.
This is where it gets interesting: despite the show obviously distinguishing between the bad and the good guys, within each of the two groups are different shades of "evil" or "good" or a mix of both. It's interesting to see characters grow and learn from one another, or the opposite, seeing them bringing the worst out of each other (evil and evil makes super-evil). Here are the main character ranked by their moral compass.
Hughie
Hughie certainly is the most good-hearted character among all (considering that a huge majority of them are either deeply rotten or have vague, ambiguous morals). He cares about people and not just the people he loves. His heart doesn't know evil even though he might not be perfect; no selling himself, no compromising his morals, no hurting people in the process. He's the kind of person who always looks for a peaceful way to deal with conflict.
Rebecca
Rebecca, Billy Butcher's long-lost wife, ranks in second place as the most good-hearted person on the show. Although it's a fair competition between Hughie and Rebecca when it comes to who is the most good-hearted one on the show, Hughie still looks like the purest and most innocent. Rebecca, however, isn't that different as she's compassionate, understanding, extremely resilient, and altruistic.
Starlight
Starlight, also known as Annie January, is one of those characters that brings a certain sense of comfort, perhaps because she's always good, kind, and looking to make the world a better place.
The reason why she ranks third is that, as she admits in season 2 to Butch when comparing herself to Hughie ("he's too good, for both of us"), she is a bit better at "doing what it takes" if that helps to achieve the mission's goal. Despite this, her actions are often good. It's also understandable why her moral compass would be compromised after what she went through.
Mother's Milk
Mother's Milk also proves to be one of the most morally balanced individuals of the show. He's not completely innocent of crimes and misconduct, but many of the things he did were a result of what Compound V did to him. Still, he's always on the good guys' side and would never harm an innocent person. Before rejoining the Boys in the battle against Vought and The Seven, he used to work in prison to help redeem those in need. He has the best interests of his family at heart.
Frenchie
Frenchie is initially presented as a dark, dysfunctional character, but as the show progresses the audience gets to know him better. He has done some bad things and taken some bad roads. At some point in the show, the main reason Mother's Milk hated him was revealed: he held him responsible for the death of children that he had to save. However, Frenchie explains the difficulties of the situation and that if he could've done better to save them, he would have. He is a good guy deep in his heart, and this side of his often comes out concerning Kimiko.
Butcher
Billy Butcher is a pretty hard character to define by the parameters of good and evil or right and wrong. Perhaps because he often seems like a mix of both.
However, Billy seems to lean on the good side more than the bad. There's no denying that he's problematic, obsessed with suppressing his emotions, and has anger issues, but he can tell right from wrong and he still isn't capable of hurting innocent people (even when he himself doubts it). He is part of the good guys, but he's flawed.
Queen Maeve
Queen Maeve is also a difficult character to define in terms of ethics and morality. Sure, she's part of The Seven and has been an accomplice to many crimes, but she often had no other choice left. Like all the other superheroes, she was created and forced into this superhero role. Perhaps unconscious of Vought's real intentions, she slowly started showing signs of remorse. It's also important to point out how often Homelander coerced, blackmailed, and threatened her into going along with his crimes. Yet, at the end of season two, she saved the whole situation by putting Stormfront and Homelander back in their place. Perhaps she's not the most good-hearted one, but she's working on it.
A-Train
A-Train ended up being useful to The Boys and their mission just like Queen Maeve, however, his motives were much more selfish.
Sometimes he sounds remorseful or like he'd prefer to not follow Vought' and Homelander's orders, however, he never does commit to it. He killed his own girlfriend whom he claimed to be in love with, saying that he had no other choice, but he did. Perhaps more character development is on his way in the next seasons.
Homelander
Homelander is considered the biggest threat of all in the show. After all, he's the strongest Supe of all and could destroy the whole planet if he wanted to.
Sure, he's one the evilest characters of the show, but he was turned into this by other people. Inside of him there's just a hurt child, so hungry for validation and blinded by his need to be loved, that all it takes to tame him down is to threaten to take those things from him. What makes him so dangerous, however, is that he doesn't care about getting better and only allows people to exist to love him.
Stormfront
Despite all that's been said about Homelander in the show, has he really been the evilest character of all in the first two seasons? Stormfront seems even fuller of hatred and hunger for power than the rest of the Supes. She's a hundred-year-old nazi and also one of the strongest Supes (in the Seven), whose only goal is to create a new race to serve her and Vought's higher purpose. She has no interest in fixing her broken self and ego, nor does she have any redeeming qualities.