The Byzantine emperor Justinian was the sole ruler with complete authority. How did this differ from feudal monarchs in Western Europe?

The sole rule with complete authority of Justinian in Byzantine differed significantly from the way the feudal monarchs in Western Europe, and this can be most easily seen in the fact that while Justinian's word and wish were law and there wasn't anyone that can oppose him, in Western Europe, the feudal monarchs did not had this power because there were multiple people in the country that had a regional power and their own armed forces so the feudal monarchs had to be in good relations with them and discus every move with them because they could turn their backs on him and give him big troubles in every aspect.