The Black Death transformed European society by killing half of it

Between 1347 and 1351, the bubonic plague killed an estimated 30–60% of Europe's entire population — roughly 25 million people. The immediate consequence was labour scarcity so acute that surviving peasants could demand wages for the first time, accelerating the breakdown of the feudal system. Landowners who refused were simply ignored as workers moved to better conditions. The Church, unable to explain the catastrophe theologically, lost significant authority. Historians broadly agree that the Black Death compressed a century of social change into five years.

Source: Ziegler, The Black Death (1969)