Final answer:
Prince Klemens von Metternich was the most important official at the Congress of Vienna due to his role in shaping decisions, guiding negotiations, and maintaining the balance of power in Europe.
Step-by-step explanation:
The most important official at the Congress of Vienna was Prince Klemens von Metternich, the Austrian foreign minister. He played a crucial role in shaping the decisions made at the Congress and was a driving force behind the conservative principles that guided the negotiations. Metternich's influence was significant in maintaining the balance of power in Europe and suppressing revolutionary movements.
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