What are Pope Benedict XVI's greatest accomplishments?

Answer 1

He published many books, he worked hard for the complete reunification of the Society of Saint Pius X with the Church. Pope Benedict XVI issued a Moto Proprio allowing Mass according to the Missal of John XXIII to be used by any priest. He set up a mechanism for Anglicans to return to the Church, and for Anglican priests to come into the Church and be ordained as Catholic priests even if they were married. He corrected the translation of the Novus Ordo. He corrected the translation of the Catechism of the Catholic Church. He pushed to reorient the Mass correctly with the priest facing God and not the people. He pushed to get the people to start receiving Holy Communion on the tongue while kneeling. Overall, his two main goals were to reorient the Church with a hermeneutic of continuity with the pre-Vatican II Church and stop the abuses which have cropped up like weeds, and to educate the priests and faithful about the Catholic faith. He made an effort to appoint solid, Catholic bishops. He was a breath of fresh air after the protestant heresies of the past 45 years have mutilated the Church.

Answer 2

Blessed Pope John XXIII surprised everyone by calling for an Ecumenical Council to "update" the Church. It was the first such Council since the Council of Trent was called five hundred years earlier.