Her most famous opponent was hades. Legend says that her daughter Persephone, was snatched by Hades. Demeter searched for her but couldn't find her so she stopped all life from growing on Earth.
My opinion on Demeter is that she was very loving, and caring for her daughter. She had lost her daughter so she went to go try to find her. Although she didn't find her, she would get to see her every spring. I think that all the stuff she did was brave.