This according to WikiProbably. And old Leon never had much problem with mass killing and torture either.
From Irish perspective, Brian Goold Verschoyle was abducted by NKVD in Barcelona and taken back to Moscow. He died in gulag.
Can't recall immediately what his crime was. Think he had married a Russian woman.
The flash point was a disagreement with the Soviet ambassador in Valencia, for whom he was working. His increasing anti-Stalinist views may have been a factor in his split with Moscow, as he quickly realised the Soviet Union had no interest in a world revolution which would be independent of Moscow's control. His letters to his family in Ireland reveal a growing sympathy for the anti-Stalinist Workers' Party of Marxist Unification (POUM).
In April 1937 he was asked to report to Barcelona harbour to repair a ship’s radio. When he embarked he was escorted to the radio cabin and the door was locked behind him. He had in effect been kidnapped and when the ship arrived in USSR he was immediately transferred to the Lubyanka (KGB) prison in Moscow. He was eventually sentenced to eight years for counter‑revolutionary Trotskyist activities. https://en.wikipedia.org/wiki/Brian_Goold-Verschoyle
Interesting RTE documentary on the Gould Verschoyle brothers.
Edit: just noticed that the link did not work, http://www.rte.ie/tv/fleshandblood/gooldverschoylefamily.html
"Flesh and Blood", if you are interested, a google search will bring you to a site where it can be wathed