Admiral Ozzel

Admiral Ozzel was the Officer in charge of"The Imperial Death Squadron" 
a taskforce consisting of Vaders Super star destroyer and5 imperial 
class star destroyers.(The goal of the taskforce was to locate and
destroy the rebels in retaliation for the death star) Admiral Ozzel 
died at the hand of Darth Vader after he in his overconfidence 
brought out the taskforce from hyperspace to close to the Rebels.
His misstake gave the Rebels time enough to prepare an escape/defence.