Most everyone focuses their attention on having compelling protagonists. But are you giving your antagonists the attention they deserve? Whether you're writing romance, mysteries, or fantasy novels, your bad guys need to be well-rounded to be interesting. Two ways to do this are through sharing their back story and identifying the motivations for their actions.
Barbara Hinske's author website -- https://barbarahinske.com/
J. W. Judge's author website -- https://jwjudge.com/
J. W. Judge's writing blog -- https://expectantwriter.com/