Magua, the vengeful Huron "wily fox" is the antagonist in the novel, though in a wider sense the true antagonist is the destruction or diminution of the noble Indian way of life by the incursions of whites into Native American territory.
Magua, who can manipulate people easily, wants revenge on Colonel Munro for beating him for drunkenness. Magua, a proud man, felt humiliated by the colonel. Knowing very well the racial code of the whites and their racism toward the natives, Magua decides to hit the colonel where it hurts: by marrying his daughter Cora. Magua therefore kidnaps and at first terrorizes Cora. He becomes the face of white fears of interracial marriage and Native American rape of white women.
Magua is a complicated character because although he is humiliated by his treatment in general at the hands of whites, who beat him, take his land, and treat Native Americans with disrespect, he is also an opportunist who puts gains before honor. He wants to be understood as a man who takes revenge because his honor has been violated, but honor is not always his first concern.
Magua is also complicated because, although clearly a treacherous villain, he also comes to genuinely have compassion towards Cora, and while he threatens to kill her, he never does.
Magua represents the degradation of the Indian soul through contact with whites. His kidnapping of Cora and her sister is wrong, and although he does not kill Cora, another Huron does. In the end, Hawkeye's killing of Magua enacts justice.
Hawkeye represents the best of the white culture trying to build bridges of understanding between whites and natives for pure hearted reasons. Magua is his opposite, sowing dissent and breaking bonds for selfish reasons and doing so through underhanded means.
Mohicans Uncas and Chingachgook are noble Indians. Uncas is in love with Cora but works to save her and dies at the hands of Mugua. Both Uncas and Chingachgook are positive characters who are friends with Hawkeye and have kept to the old, honorable ways of their tribe. They have not turned to evil as has Magua.