Exodus 9:14 For I will at this time send all my plagues upon thine heart, and upon thy servants, and upon thy people; that thou mayest know that there is none like me in all the earth.
God sent the plagues on Egypt to show them that He was God and there was no other like Him. He is and has always been the only true God. The plagues attacked the false gods of the Egyptians and proved that God was truly God.
God is eager for all the world to know that He is the One and true God. He calls on us to witness to His power. As we live out the new life that He has put in us then we are giving the world a testimony of our good and great God.