What to do about a former supervisor?

You need to talk to the former supervisor at your last job which you used as a reference. Did they know you were listing them? Perhaps instead of using the former supervisor, you can use your istant manager or coworker at the last job or even an outside client or someone else who will portray you in a positive light. Another alternative is to visit an employment lawyer and have them send a cease and desist letter to your previous employer. Hopefully that will be the end of it. If not, your lawyer will have some ideas.