An example of previous action would be the violent supression of the Prague Spring of 1968 under Brezhnev
Not a full answer, but my recent post on the Soviet Union's collapse might help to nuance your understanding of the role of violence in the late Soviet era. There were outbreaks of repressive violence during the Gorbachev era, despite the fact these were not as large in scale as those seen under previous Soviet leaderships. Vladislav Zubok's recent book Collapse: The fall of the Soviet Union (New Haven: Yale University Press, 2021) is very good on this.
Malcolm