Examine the morality of M. Thenardier and M. Javert.
There is a thorough character anaylsis here at Enotes. Here is an excerpt on both Thenardier and Javert that speaks to their morality (or lack thereof). I have "bolded" the parts that speak to the morality issue.
Monsieur Thernardier is "(t)he unscrupulous innkeeper and his wife take care of Cosette, but treat her poorly. He embarks on a life of crime, getting involved with the worst criminals in Paris, and attempts to entrap and rob Valjean. Although he ends up in prison, he escapes. He helps Valjean escape from the sewers when Valjean is trapped there with Marius. Thenardier plays a central part in the plot. He does good in spite of his evil intentions, not knowing what the consequences of his own actions will be.
Javert serves as Valjean's nemesis throughout the novel, continually threatening to expose his past and bring him under the control of the law. In his exaggerated, nearly fanatical devotion to duty and his lack of compassion, Javert represents a punitive, vengeful form of justice.
You can find out much more about these two characters by visiting the link below.