The greatest Prime Minister of Canada was? Mackenzie King our 10thPrime Minister of Canada and by far one of our greatest. William Lyon Mackenzie King accomplished a lot in his twenty-0ne years of ministering our Country Canada! "It is what we prevent, rather than what we do that counts most in Government." (Mackenzie King august 26, 1936) This statement sums up the best secrets of Mackenzie King's success as prime minister, and perhaps, the key to governing Canada effectively. King's record of prime minister is sometimes difficult to judge. He had no uninteresting images, he gave no repetitive speeches, and he champions no drastic stage. He is remembe