Constantine.

The emperor Constantine has rightly been called the most important emperor of Late Antiquity. His powerful personality laid the foundations of post-classical European civilization -- his reign was eventful and highly dramatic. His victory at the Milvian Bridge counts among the most decisive moments in world history, while his legalization and support of Christianity and his foundation of a 'New Rome' at Byzantium rank among the most momentous decisions ever made by a European ruler. …

…rivals, including the fourth Caesar, Flavius Dalmatius, had been eliminated in a bloody coup. This bloody purge of members of the Royal family, it has been argued, may have had its roots in the religious strife between the Arian and Orthodox factions at the imperial court. In the Eastern Orthodox churches Constantine is regarded as a saint -- he shares a feast day, with his mother, and additionally has a feast day of his own.