Which is a reference to a great victory? Atlantis Gettysburg Waterloo Austerlitz

Actually, there has been two battles in the choices provided that could fall into a "great victory", these are the Battle of Gettysburg and the Battle of Waterloo. The Battle of Gettysburg was known to be the most "costliest" battle at the course of the American Civil War, and on the other hand, the loss of Napoleon in the Battle of Waterloo led to the great French Empire's demise.