Answer: Lech Walesa is known as the leader of the massive Polish anti-communist movement SOLIDARNOSC (Solidarity) that was established already in 1980. Lech Walesa is a person generally associated with the end of Communist order in Poland in 1990.
Explanation: of course there are other personalities and wider context we have to take into consideration - 1) history of USSR and presidency of Gorbatchev, 2) fall of the Berlin War, 3) negotiations Gorbatchev - Reagan etc etc.
