Besides the English language, did they make any other lasting contributions to Western civilization?
I often say the Vikings introduced the Western world to death and taxes. Their raids obviously killed a lot of people, and when they attacked, Europeans realized they had to shape up to repel them. That meant kings had to raise money, and after they got what they could from the Church, they had to start taxing the people. The Norse invaders were determined to get what they wanted, and they continued to demand more and more both by threatening to strike and by kidnapping and charging enormous ransoms. Churches became impoverished. In 994 they threatened to burn down the Canterbury Cathedral unless the archbishop paid them off with a large sum of money. The archbishop, who a few decades earlier had controlled the most wealth in England at the time, had already paid them so much that he had to borrow money from another bishop.
Their constant threat also inspired kings to get their military organized.