Question

The Byzantine emperors deeply resented—as an affront to their dignity—the pope's imperial coronation in the year 800 of the Frankish king,

Answer 1

Answer: Charles the Great.

Step-by-step explanation:

Charlemagne has crowned Christmas in 800 AD. The ecclesiastical question was the most important in Europe in those decades, and Charles the Great was the most capable ruler in Europe.

Consequently, the pope turned to the ruler of the enormous European Empire at that moment. Some historians also call him the "Greatest Christian of all time."