Who was Pope St. Leo the Great and what did he do?

Throughout the 2,000-year history of the Catholic Church there have been a variety of popes who chose the name Leo, but only one has come to be referred to as "Leo the Great."
This title is typically given to a saint
"The Great" is not an official title that is awarded by the pope or the Vatican, though at times this may happen, as with Pope Benedict XIV who was the first to call St. Gertrude of Helfta "the Great."
Generally speaking it is a "popular" title (not an official one), given to an individual by the people, who all agree about the greatness of the person.
St. Leo the Great
The only Leo to be called "the Great" is
The
One of the most famous episodes from his life was his encounter with
When Northern Italy had been devastated by Attila, Leo by a personal encounter with the King of the Huns prevented him from marching upon Rome. At the emperor's wish, Leo, accompanied by the Consul Avienus and the Prefect Trigetius, went in 452 to Upper Italy, and
This highlights St. Leo's desire for …