1991 August Coup
The last event that brought to the dissolution of the Soviet Union, the August Coup lasted for 3 days in August 1991, from 19th to 21st August. In an attempt to restore the Communist Party to full power, a coup (violent and illegal seizure of the government) was launched. The motive was to force Mikhail Gorbachev to resign and his reforms to make the Soviet Union. more open to be removed.
However, despite tanks in Moscow's streets, the coup failed and it saw a plethora of things happen like Ukraine declared its independence while Estonia and Latvia restored their independence. Communist Party of the Soviet Union was dissolved which eventually led to the dissolution of the Soviet Union in December.
Power still switched to the republican elite with President Mikhail Gorbachev left with effectively no power. The failed Coup led to the rise of Boris Yeltsin who later became Russia's first president. As this was going on, all the TV stations in the Soviet Union played a video of the Swan Lake ballet for the 3 days that the coup was on since news was forbidden. Almost fitting as the term swan song refers to someone's last act before they die.