Bela Karolyi, the embattled yet successful gymnastics coach who helped young women vault to the highest levels of the sport in the Olympics, has died at the age of 82, USA Gymnastics has announced.

Legendary and controversial coach Béla Károlyi, who died on Friday, played a key role in transforming USA Gymnastics into an Olympic and international competition powerhouse, turning out superstars like Kerri Strug and Nadia Comăneci.

Bela Karolyi and his wife Martha defected to the U.S. in 1981, and over the next 30-plus years, became a guiding force in American gymnastics, though not without controversy.