There are two basic dangers that hurricanes bring: wind and flooding. Both can be extremely destructive, as we have little which we can use to battle these forces of nature. By comparison, if we were to drop an atomic bomb, we would find that a hurricane can expend as much energy as somewhere between 10,000 and 500,000 nuclear bombs!
Hurricanes are one of the worst categories of natural disasters we can encounter. Only tsunamis and the stronger earthquakes tend to cause more widespread damage. But, while earthquakes are more common that hurricanes, the stronger ones are actually quite rare.