The perspective that a European living in a country conquered by the Mongols is most likely to have is: The Mongols were responsible for the murder of millions of people in their conquest of European countries.
This viewpoint reflects the immediate consequences of the Mongol conquests, which were often marked by violence and destruction. While the Mongols did have a significant impact on trade and the exchange of knowledge across regions, a European witnessing the devastation brought by the conquests would likely focus more on the immediate suffering and loss of life.