A final crushing defeat can be described by the two crossword solutions of WATERLOO (8 letters) and ROUT (4 letters). WATERLOO is a small town in Belgium that was the site of a famous battle in 1815 between the French army, led by Napoleon Bonaparte, and the British-led coalition forces. The battle ended with a decisive victory for the British-led coalition forces, resulting in a final crushing defeat for Napoleon and his army. The term 'ROUT' is used to describe a complete and utter defeat, which is what happened at WATERLOO.