iron will

An intense, unbreakable sense of determination and purposefulness. With ruthlessness and an iron will, the businessman built a media empire that now includes the majority of broadcasters around the world. Despite the setbacks in her life, the athlete has time and time again displayed an iron will in her quest to win an Olympic gold medal. My toddler has an iron will, and it's darn near impossible to get her to do anything she doesn't want to do.