Amanda is only the antagonist if you think that Tom is the protagonist. Even then, she’s more a pain in his side than that a villain. But we’ll make the argument anyway. Amanda harasses and badgers Tom into being unhappy and restless. She begrudges him small pleasures like drinking and going to the movies, and she insults him for wanting to be happy himself instead of looking out for his family. The question is, does this make Amanda merely a concerned mother, or is she a legitimate antagonist?