Final answer:
The political unrest in Eastern Europe was sparked by the rise of the Solidarity labor union in Poland, which organized strikes and threatened the communist government. This movement eventually led to the collapse of Soviet Union power and communism in Eastern Europe.
Step-by-step explanation:
The political unrest in Eastern Europe that was sparked by the rise of a powerful Polish labor union was called the Solidarity movement. Solidarity was an independent trade union formed in Poland in the 1980s, led by labor activist Lech Wałęsa. The movement organized strikes and demanded political change, threatening to bring down the communist government. Solidarity gained momentum and eventually led to the collapse of Soviet Union power and communism in Eastern Europe.