My guess is Rutherford. He utterly changed Russell's ideas in the areas of "doctrine" and "organization". None of the others who followed introduced the massive turnaround that he achieved.
Imagine what it would be like if someone were to take the present "teachings" and "organization" and then return these to those which existed under Russell. That would give an idea of the enormity of what Rutherford did.
Even today, the WTS worships Rutherford's 1919 experience as being "the moment" when Jesus selected them out of all people on earth. It worships Rutherford's inventions, such as: the name "Jehovah's witnesses", the identification of "the Great Crowd", and the "theocratic" arrangement. Who else has made such sweeping changes? Rutherford dropped Russell's key focus on the Return of the Jews to Palestine. Russell was lauded as the most influential Christian Zionist. It was a key plank in his Divine Plan.
Even the "no-blood" doctrine, although opening up in 1945 under Franz, had its genesis in the quackery that existed in the 1930s under Rutherford's watch.
That's my opinion. Known to be wrong before,
Doug