My belief is that it is the relationship between the client and the therapist is the catalyst for change and determines the success of therapy.
Therapy modalities and therapeutic techniques are critical, of course, but how the therapist and the client use these is what makes for change.
I find that as a result of 33 years providing therapy; Cognitive Behavioral Therapy works best. It gives clients more control over their thoughts, feelings and actions. And again, it is the therapeutic relationship that leads best to success.