I'm going to give bad feedback about my clinic supervisor behind their back
What is your reason for doing it behind their back?
I'm still waiting for them to do their job, I just want to shoot them down for all the mistakes they have made.
It is wrong to talk about people and disparage them behind their back. If you have a problem you should confront them directly and not be petty about it.
Fuck, I just wanted to get them mad and have them realize how terrible they are.
Well if this is the case, telling it to their face would be the more moral thing to do. In addition to that, it would give you a chance to see how they feel about the bad feedback you are giving. Sometimes this is more helpful to get someone to change their behavior.