Wide Sargasso Sea
Since the novel never tells us who's telling the truth, we're giving Antoinette the benefit of the doubt here and calling this character Daniel Cosway/Boyd. Claiming to be the illegitimate son of Mr. Cosway and one of his slaves, Daniel sends a spiteful letter to Rochester with the intention of destroying Antoinette's marriage and blackmailing Rochester to keep the scandal quiet. While at times Daniel puffs himself up as an educated and moral man, at other times he debases himself before Rochester and embraces the idea that he's an intellectual inferior because of his race. The blend of self-aggrandizement and self-hatred makes this character a particularly vivid example of the twisted logic of racist thinking.