Which is the most influencing factor w.r.t. Quality Assurance?

Your question addresses Quality Assurance specifically. QA is a subset of Quality Management as is Quality Control.

QA, as defined by ISO 9000 is: "part of quality management focused on providing confidence that quality requirements will be fulfilled". Essentially QA is a verification/confirmation that the Quality Management program is effective thus will achieve customer acceptance. The project Quality Management program would include the QM of all contributors to the project. The final QA then is a validation that all QM programs are appropriate and are being implemented effectively. This is primarily achieved through process and templates

Thank you peter for your response.
But you might have missed to read through the thread description.
This thread is created to check what experts think about most influenching factor among following :

-Testing method and test coverage.

-Process and templates

-Requirement Analysis

-Customer acceptance.

Tarun; I chose "process and templates" and gave you my reasons as requested in one of your earlier responses. What did I miss?