<p>I'm sure it isn't Butakha. the owner of the pro-bending arena. although it's seem he may know who founded the sport. Every Sport even in the "real world" has its own humble beginnings. Pro-bending may have existed even in ATLA. though the atla comics may say otherwise. but i can see bryke or gene yang putting a hinted easter-egg in the later atla comics about pro-bending. But we know that pro-bending existed even when korra was a child. She confirmed herself that she would listen to the radio program that broadcast pro-bending matches. </p><p>My predicting theory is this: Maybe Avatar aang and his crew would encounter some benders playing a game they never seen before....which is now called "pro-bending" during the early days of republic city. </p><p>HELL! maybe a non-bender created pro-bending! that would be cool. </p>