Bela Karolyi, the polarizing U.S. gymnastics coach who mentored Olympic champions while leaving broken bodies and minds in his wake, died Friday, USA Gymnastics announced. He was 82 years old.

No cause of death was provided.

Given how successful U.S. women have become at the Olympics in gymnastics, it’s easy to forget how long they had to wait to find victory at the Games. With the Soviet Union and Eastern Europe dominating the sport for decades, no American woman won an individual gold medal until 1984 at the Los Angeles Games, and the U.S. didn’t win the team gold until 1996 in Atlanta.

Karolyi and his wife, Marta, were central figures in that breakthrough and subsequent rise. The couple defected from Romania in 1981, when it was under the rule of dictator Nicolae Ceaușescu, and arrived in the U.S. with immense clout in the gymnastics community via their tutelage of Nadia Comăneci, a five-time Olympic gold medalist and the first gymnast to score a 10.0 at the Games.

Comăneci posted a tribute to Karolyi on Instagram:

The Karolyis quickly found more star pupils in Mary Lou Retton, Julianne McNamara and others. With the Soviets boycotting the 1984 Olympics, Retton became the first American woman to win the Olympic all-around event, while McNamara won the uneven bars.

Retton’s win in particular was a star-making performance for both gymnast and coach. While Retton became an American hero, Karolyi cemented himself as the top personal coach for Olympic hopefuls. That was also when he started to become a controversial figure, often clashing with USA Gymnastics officials over guidance of their shared athletes.

Karolyi demanded everything from his students, most famously in 1996, when he had an injured Kerri Strug perform one more vault to seal that first U.S. team gold. Strug landed the vault, instantly shifted her weight to her good foot, saluted the judges, then fell to her knees. Karolyi later carried her to the Olympic podium.

Karolyi became the national team coordinator for USA Gymnastics in 1999, but his tenure was short. His strict tutelage led to public pushback from the gymnasts, with no Olympic success to show for it at Sydney in 2000. Marta later took over the job, which she held until 2016 with great results.

USA Gymnastics is now a juggernaut on the women’s side, winning the last six Olympic individual all-around gold medals and three of the last four team medals. There is no separating Karolyi from the organization’s upward trajectory, but there is also no denying his methods reflected the darker side of the sport.

His reputation has not aged well, to say the least, even as his most famous pupils continue to defend him. In 2018, other former gymnasts described a toxic atmosphere at USA Gymnastics under the Karolyis, with young girls starved and worked to the point of delayed puberties. It was also in that environment where Larry Nassar was able to thrive as a sexual predator, preying on girls until dozens of them stepped forward beginning in 2016.

Karolyi leaves behind one of the most complicated legacies a coach can have. He played a central role in both the best and worst parts of USA Gymnastics, and all of those gold medals came at a price that people other than him had to pay.