How is the theme of morality present in A Tale of Two Cities?

In A Tale of Two Cities, Dickens presents three very distinct groups of characters: the good, the bad, and the comic. Each is a caricature, rather than real-life characters. As far as the first two groups, the good are almost impossibly good, while the bad are almost impossibly bad.
The bad, such as Madame Defarge, have no evident redeeming qualities. Her heart is black with hate and revenge, due to the murder of her family. She has given herself completely to the destruction of the nobility, personified by Charles Darnay and his family, since it was Charles’s father and uncle who caused her family members’ death. She shows no mercy to anyone. She joins in the killing spree after the Revolution begins. The notions of “freedom, equality, and fraternity” have no real meaning for her. Her only motto is hate and kill. She has become a caricature of the immoral being. She remains in this static character throughout the story.
Doctor Manette and Lucie, as well as Charles, are seemingly without major flaws. They love each other and do not seem to be able to have the kind of hate that Madame Defarge has. While Doctor Manette had felt this hate while confined in the Bastille, he has renounced it. He lives only to love Lucie and Charles. This group represents the moral individual, who return hate with love.
It is Sydney Carton that is the most realistic character, showing a moral battle in his heart throughout the novel. At the beginning, he is lazy and dissipated, of very little worth to anyone. He is not evil, however, just deeply flawed. Once he falls in love with Lucie, even if it is unrequited, he begins to turn his life around to a limited extent. He promises to do anything to save her or anyone she loves. He chooses in the end to sacrifice himself, which can be described as the highest moral good that anyone can do. It is through Sydney Carton that the theme of morality comes forth as a living struggle.