Is it ever possible for an attorney to negotiate a severance/separation agreement without filing with EEOC or one of the agencies?

This employee had to endure harassment (based on a protected characteristic) from different people hold positions in management. The client wrote a formal complaint but the investigation was a whitewash. Over 3 months since the investigation and nothing has been said regarding the conclusion. Even after the complaint; the employee still encountered the same problem. Due to the way management treated this employee; the employee had to deal with hostility from other workers which was the result directly from management actions. One of the persons listed in the complaint was one of the main people conducting the investigation. They never wanted to reach a conclusion because management was involved. This employee had to suffer for months on end. It didn't stop after the complaint and more should've been done. Besides the first questioning after the employee filed the complaint no follow up questions was asked. This person was never asked about any evidence or anything. There is so much evidence of how this person was treated poorly to similarly situated employees (working directly with this person) who didn't share the same protected characteristic. They were interested in finding the truth because it would've implicated the higher up people in management. The employee was even prohibited from taking part in certain employment terms and conditions.