I'm wondering if this phrase can be used to characterize two characters, one who is morally good and one who is bad. Specifically I am trying to say that "I want to examine character A and character B because, through their morally dialectical representations, they reveal... etc"
Judging from your comment back on January 14, I think you're using the term "dialectical" correctly, but "morally dialectical" is clunky usage.
Dialectic implies being in opposition, yes, but it also means being in dialogue with one another. So the two women you describe: if they are characters in the same book and they interact, interpreting and critiquing one another's morality, then they have a dialectic relationship and are already in a dialectic conversation that you can explore.
But if they are characters in different stories and you just want to compare and contrast them, go ahead and "compare" and "contrast" them— that's not dialectic.
However, you could create a dialectic relationship between them, as an academic writer, by posing them together in your discussion of their morality and morality in general. I wouldn't say you're putting them "in opposition" to one another: to create a real dialectic, the term "juxtaposition" may be more helpful.
So you take a situation from one book or the other, or a situation from current events or common knowledge, and you put each character "in character" in that situation, and imagine how each one would respond. Then you do the magic of dialectic, and you imagine how each would comment on and respond to what the other one did or said.
This is purely hypothetical, of course, so you need to be comfortable writing significant parts of this in the subjunctive, at least while you are setting the dialectical stage. Once you've got the two characters in dialogue, then you can continue in present or simple past tense as usual.
Don't "just write a scene" with tension and conflict, though. That's not deep enough for dialectic analysis. Comment (or speculate) on why each one sees the situation the way they do, how each sees the other the way they might, how each one perceives the moral texture of each act and word, each attitude and motive, of the other. This can be done entirely in academic analysis or by nesting a creative scene within your academic essay, whichever appeals to you.
Dialectical analysis is a lot of work, but highly rewarding if you can pull it off. You'll learn a great deal yourself. And you may accidentally develop a fascinating one-act two-person play or skit that will be really deep (though of course you hide the dialectic analysis behind their spoken dialogue and action, perhaps reveal some of it in a judicious monologue).
True dialectic tries to be fair to both sides, of course. This will be easier since, as you say, they are not really diametrically opposed, they just see things and do things differently ...but these are moral things involving social mores. We're not talking about preferences of ice cream flavors. That's what makes them interesting, and possibly meaningful in a helpful way to your readers or listeners.
I hope this is helpful.
I do love a proper dialectic encounter.