Creating Believable Characters on the Page--Tips for Fiction and Memoir Book Writers

I've been struggling with my antagonist. That might sound like a normal situation--antagonists create conflict--but my challenge is less about what he does than how believable he is on the page.

One editor told me:  "He's too much like the other nasty guy."  Another said, "It's just Bad and Badder."  My agent said, "The antagonists need to be as believab…