Meg Murry is the protagonist and arguably the biggest "fighter" in the story. She is determined, resourceful, and never gives up, even when facing overwhelming odds. Her fight is against darkness, fear, and despair. She confronts these forces head-on, using her courage, love for her family, and unwavering belief in good to overcome them.
Charles Wallace Murry is also a "fighter" in his own way. Despite being a young boy, he exhibits incredible intelligence, psychic abilities, and an unyielding belief in love and truth. He fights against the forces of evil by using his mind and his connection to the universe.
Mrs. Whatsit, Mrs. Who, and Mrs. Which are powerful beings who fight for good. They use their wisdom, knowledge, and supernatural abilities to help Meg and her companions navigate the dangerous journey to find Charles Wallace. They fight against the darkness by illuminating the path of hope and guiding others to the light.
Calvin O'Keefe is a strong and supportive friend to Meg, who helps her fight for her family. Although he doesn't possess supernatural powers, his presence and unwavering belief in Meg provide her with strength and courage.
Therefore, a "fighter" in *A Wrinkle in Time* is not confined to a particular character type. It encompasses those who actively resist the forces of darkness, challenge societal norms, and fight for love, truth, and light. The key attributes of a fighter are courage, determination, and unwavering belief in good.