Henry Kissinger famously (and apocryphally) once asked, "Who do I call if I want to speak to Europe?" Today, the answer is Mario Draghi, president of the European Central Bank, whose influence on the euro's survival makes him Europe's most powerful person. Since becoming ECB chief in late 2011, the 65-year-old Draghi has aided troubled euro-zone banks with $1.3 billion in ultra-cheap loans and has overseen a massive bond-purchasing plan for debt-groggy countries under market attack. Now he's preparing unified supervision of all euro-zone banks. If the currency survives as a result, the entire world will call Draghi with its thanks.