The clause that angered German citizens in the Treaty of Versailles was the one that forced Germany to take responsibility for the beginning of World War I. Since this was war was considered Germany's fault, they now had to pay reparations to Britain and France, reduce the size of their military, and loss colonial possessions.
This angered German citizens, as it made Germany a much weaker nation and resulted in the crash of the German economy. These punishments would lead to hyperinflation and the awful time period known as the Wiemar Republic, in which Germany struggled as a country for over a decade.