Answer:
The fatal obstacle to German unification under Prussian leadership in 1850 was the opposition of Austria, which had long been the dominant power in the German Confederation. Austria, along with several other German states, viewed Prussian leadership as a threat to their own power and influence in the region.
The idea of a united Germany had been gaining support among German nationalists in the mid-19th century, and many saw Prussia as the natural leader of a unified Germany. Prussia had a strong economy, a powerful military, and a commitment to modernization and industrialization.
However, Austria was a major obstacle to this plan. The Austrian Empire was a multi-ethnic state, with a large German-speaking population, and it viewed itself as the natural leader of the German-speaking world. The Austrian government feared that a unified Germany under Prussian leadership would threaten its own power and influence in the region.
These tensions came to a head in the Frankfurt Assembly of 1848-49, which was a meeting of German nationalist representatives from across the German Confederation. The Assembly was divided between those who supported Prussian leadership and those who supported Austrian leadership, and it ultimately failed to reach a consensus on the issue of unification.
After the failure of the Frankfurt Assembly, the German Confederation remained divided and the prospect of German unification under Prussian leadership remained distant until the 1860s, when Prussia was able to build a coalition of allies and defeat Austria in the Austro-Prussian War of 1866. This victory paved the way for the formation of the North German Confederation under Prussian leadership, which was a significant step towards the eventual unification of Germany in 1871.