Charlemagne (Charles the Great)
In my opinion, Charlemagne accomplished many beneficial things for the church and deserves the praise he has received for his actions. Although not everything he did was perfectly Catholic, in general his intentions were good. He achieved much more than previous empires in terms of uniting Christendom and protecting the Pope.
It's interesting to note that Charles was not next in succession for the kingship. His father Pepin, had given Pope Zachary the Papal States, so in return the Pope granted an edict that declared descendents of Pepin's bloodline would continue to rule. This close relationship between king and Pope would be maintained when Charles assumed the crown. If this had not been true, Charles would probably not have been able to carry out many of his military campaigns against the Saxons to the north. In addition, I don't think he would have had such successes had he not inherited the kingship as practically a child and experienced the rigors and strategic elements of military life form his father's numerous campaigns throughout Europe.
I'm sure he felt the pressures of being king immediately as he inherited the title "Patricius Romanus" from his father, which required him to provide protection for the Pope and the Roman Catholic Church. This tremendous obligation didn't cause Charles to falter though; many times he sped to defend Rome from the Lombard invaders. He must have a great amount of bravery and courage to do this and also fight in other campaigns in areas around his territory. An example would be in 772, he advanced into the region of the Saxons, destroyed their capital city, and burned their most sacred pagan idol. In this way, Charles goal was to unite the Western Empire together under one religion. Since most...