One plague should have been enough to set the Israelites free from Egypt, so why did HaShem command Moshe and Ahron to do 10 plagues? The evil forces represented by Egypt and Pharoh, have 10 evil forces themselves - just like we have 10 Sfirot of holiness, the evil forces of 10 Sfriot of evil powers. Each one of the 10 plagues destroys one of the Sfirot from the evil forces. Once when all the evil forces are destroyed, they will be eradicated completely.