Geopolitical events are always work of many, but the end of the Cold War was above all the decision of one man – Mikhail Gorbachev. He made the ending much better than it could have been for the world as a whole. For that, he deserves the world's thanks.
As things progressed, he let the Eastern European nations ruled from Moscow go their own way. Germany appreciates him for letting the East reunite with the West. With a few exceptions close to home (the Baltic states and South Caucusus) he generally avoided using violence to maintain a Moscow-ruled empire. Nations outside the USSR left the Warsaw Pact, and most became democracies. The other Soviet Republics became independent from Moscow, and generally seem to have done better than in the USSR days, but with a wide range of outcomes.
Things went badly for Gorbachev and for Russia in the early 1990s. He overcame an attempted coup with the support of frequent rival Boris Yeltsin, who thereby gained the upper hand. Yeltsin set himself up to rule 1990s Russia, while Gorbachev would be out of power as the USSR vanished under him. Yeltsin's rule was marked by economic chaos, corrupt privatizations, a return to autocracy, and the choice of Vladimir Putin as his successor.
While things in Russia went poorly, the collapse of the USSR was good for the rest of the world. Letting most of the former Warsaw Pact go its own way without a fight dramatically reduced the amount of violence that Moscow could order. The time of the US and the USSR sowing proxy wars across Asia, Africa, and Latin America came to an end.
Ending the Cold War reduced risk of total nuclear annihilation. Obviously the nuclear weapons are still there, but conflicts between two sides with big nuclear arsenals are the most dangerous, because that's where the apocalypse logic of Mutually Assured Destruction gets all the missiles in the air. Gorbachev simply disbanded one of the sides, so we're less likely now to die in nuclear war.
Overall, Gorbachev was as good a man, and much a force for good in the world, as one could hope for a leader of the USSR to be. He loved his wife Raisa. He made a more peaceful world; may he rest in peace.