“It was determined that of the 139 members and candidates of the party’s Central Committee who were elected at the 17th congress, 98 persons, that is, 70 percent, were arrested and shot […] The same fate met not only the central committee members but also the majority of the delegates to the 17th party congress. Of 1,966 delegates with either voting or advisory rights, 1,108 persons were arrested on charges of anti-revolutionary crimes”
https://www.marxists.org/archive/khrushchev/1956/02/24.htm