Just going to put this out there: it doesn’t account for every trait a character can have, but a really interesting and arguably more realistic way to look at characters (your own or otherwise) is not really that they have ‘good’, ‘bad’ and ‘neutral’ traits, but that they have a set of deeply-embedded and very durable core traits, values, beliefs, fears, desires, etc. that manifest differently according to the context. Most traits are neutral. A redemption or corruption arc would be changes to the context - which could be external, like a new person, or internal, like the character’s underlying perspective of someone or something shifting - giving the character’s fundamental traits a chance to manifest and develop in a better or worse way. You want to protect your loved ones and would do anything for them? Great! What a noble, sympathetic motivation! You think you need to kill children to protect your loved ones? …Not so great. But you still have internal consistency! Understanding a character’s core allows them to stay consistent in spite of their external and internal journeys.
To me, a strength is not quite the same thing as a virtue; a weakness is not quite the same as a vice. Virtues and vices are good and bad, respectively, in and of themselves. They will be broadly considered positive and negative in almost any situation, at least by the audience. Habitually treat innocent people like dirt, for whatever reason? Vice. Excessive cruelty is one of the most basic human no-nos. Care about people getting what they deserve? Virtue. In our minds a serial killer who kills ten random people is much worse than a serial killer who kills ten murderers and rapists with the exact same methods and sadism. Virtues and vices are moral. Strength and weaknesses are practical, and thus much more fluid. I define a strength as any trait or skill that is useful to the character, their allies and/or moving the plot in their favour. These can change from one to the other in a scene; in the presence of different company; with the character’s varying mental health. Good liar? Strength, when you’re an undercover spy. Brave? Weakness, when you need to be cautious and hold back. Selfishness can be a hero’s driving strength. Being self-sacrificing can be nothing but harmful. Unconditional loyalty can make a character the best, most helpful friend ever… to the evil psychopath. Ambition for the sake of it can motivate the classic villain to take over the world, or the hero to prove themselves and save the world.
Through this lens there’s no reason to give your villains solely immoral and unlikeable traits (aka vices) or vice versa. Because at least a substantial portion of their personality is an entirely different beast from their moral alignment. I love characters who, while still being plausibly and recognizably themselves, could have turned out on the opposite side of the moral conflict had a circumstance or two been altered. Like, in most of the infinite parallel universes of this story, they’re ‘good’ or ‘evil’ when really they’re just always them.
