Who was most influential representative in congress of Vienna?

The most influential person at the Congress of Vienna was undoubtedly Austrian Chancellor Prince Clemens Von Metternich (1773-1859). He believed that Europe would find peace only if its legitimate sovereigns were unchallenged by the forces of liberalism and nationalism, and if a single state could no longer threaten the international balance of power by becoming too powerful, as France had during the reign of Louis XIV and again during the Revolution and Napoleonic Era.

Merriman, John. A History of Modern Europe: From the French Revolution to the Present. New York: W.W. Norton & Company, 2004. pg. 602