No matter what, you will need advocates and contacts who are not your supervisor. 

Don’t put yourself in the fragile position of only being able to go to your supervisor to be the PI on an ethics or grant application. Or that they are the only person who can give you a reference.

Many people in grad school make practical decisions about their careers based on their professional networks. They may decide to work with an abusive supervisor because of the supervisor’s power and influence in their field. Although it is often in your abusive supervisor’s interest to limit or control your professional network, you are free to make whatever contacts you would like in academia. In fact, if your supervisor is not helping you to develop your professional network, there is a problem.

In every field of work, academic or not, it is “the people you know” more than “what you know” that will make you successful. This may or may not be obvious to you already. Although the premise of academia is often that talent or academic excellence is the key to success, it’s not actually the case.

Think about it like a job: you don’t need just a single, strong reference from your one boss at the last place you worked. You need at least three references from different people who have worked with you in different capacities. Don’t predicate your future success on the one bad boss (read: your supervisor). Instead, find many people who can vouch for your work and character. You might be surprised: your supervisor is not the only person who can get you the references you need. Similarly, they are not the only person who can introduce you to other people worth working with.