I think a physio needs to have good assessment skills. If you can highlight a patient's problems and pain pathway of their symptoms you can target these specifically I feel you will be more likely to succeed in treatment. I also feel you need to be empathetic yet firm with treatment. My most successful treatments/increased compliance with exercises have been when I have explained the condition and the relevance of why you are asking the patient to do those exercises(so I guess also good communication skills).