Matvei Bronstein: Theorical physicist. Pioneer of quantum gravity. Arrested, accused of fictional “terroristic” activity and shot in 1938
Lev Shubnikov: Experimental physicist. Accused on false charges. Executed
Adrian Piotrovsky: Russian dramaturge. Accused on false charges of treason. Executed.
Nikolai Bukharin: Leader of the Communist revolution. Member of the Politburo. Falsely accused of treason. Executed.
General Alexander Egorov: Marshal of the Soviet Union. Commander of the Red Army Southern Front. Member of the Central Committee of the Communist Party. Arrested, accused on false charges, executed.
General Mikhail Tukhachevsky Supreme Marshal of the Soviet Union. Nicknamed the Red Napoleon. Arrested, accused on fake charges. Executed.
Grigory Zinoviev: Chairman of the Communist International Movement. Member of the Soviet Politburo. Accused of treason and executed.
Even the secret police themselves were not safe:
Genrikh Yagoda : Right-hand of Joseph Stalin. Head of the NKD Secret Police. He spied on everyone in Russia and jailed thousands of innocents. Yagoda was arrested and executed.
https://en.wikipedia.org/wiki/Genrikh_Yagoda
Nikolai Yezhov : Appointed head of the NKD Secret Police after the death of Yagoda. Arrested on fake charges, executed.
https://en.wikipedia.org/wiki/Nikolai_Yezhov
Everybody was absolutely terrified during this period. At least 600 000 people were killed and over one million people were deported to Gulags in Siberia.
Paulus commanded a 360.000 strong army that was previously responsible for many atrocities, including mass shootings of Jews and Ukrainians at Babi Yar - one of the cruelest scenes of the war. His capture in the rank of field marshal was a major blow to the reputation of Wehrmacht command. He made the situation even worse for Hitler by switching sides and going for the Soviets, helping the anti-Hitler propaganda machine in the German ranks.
Conventional morals may question Stalin’s decision, and family values were strong in Stalin’s USSR. But he was also responsible for millions of Soviet soldiers and civilians, and any blow to Wehrmacht meant closer victory and less victims. Someone else’s sons and daughters.