Mr. Simmons, a powerful gatekeeper in the entertainment and media worlds, damaged careers and self-confidence with his pattern of sexual assault and harassment, the women say. In 1995, Drew Dixon was working her dream job as an executive at Def Jam Recordings, helping to oversee a chart-topping album and a ubiquitous single by Method Man and Mary J. Blige. But as her star rose, Ms. Dixon, then 24, was spiraling into depression, she said, because of prolonged and aggressive sexual harassment by her direct supervisor, Russell Simmons, the rap mogul and co-founder of the label.