Gorbachev has undoubtly been the major trigger in ending the Cold War, but the first real fear of death for the Soviet Union has been the popal election of Karol Woytyla in 1978. Expect for some kind of a direct coup against the CP elite, a pope coming from a Warsaw Pact state has surely been the second-worst nightmare Moscow ever could imagine and, worse, even came true.
So there has also been an assassination attempt on the Pope by Ali Agca in Rome on May 13, 1981. The two first shots were relatively harmless, but the third one went just through the intestine. Karol survived the attempt, but what if he hadn't? I still believe that Moscow and some of its satellites orded Agca to actively switch off Karol.
The pope has already been to Poland to 1980 and the Solidarnosc movement was still in full swing and the state of war was first declared in December 1981. Would there have been uprisings in Poland after Karol's death? Earlier state of war in Poland or even direct Soviet intervention? Would the history of the Cold War follow alternate paths? And who had become the next pope?