Who was the main enemy of the Normans?

The Scandinavian people were quite specific, for them it was not the main goal of unification under one flag, the main thing for them was profit and a glorious battle. Often the Vikings fought among themselves. Very often there were cases when a whole army of Varangians was hired for service or for battle in order to receive a large reward. There were also a lot of Varangians who were employed in the armies of tsars, princes, and kings. And, if you look and think, then, as such, the Varangians did not have an enemy, in fact they fought with everyone in their time.