The man who sparked the Protestant Reformation by simply wanting to discuss certain ecclesiastical abuses and inspiring other luminaries to make their own efforts at reform as a result, Martin Luther was a Confessor and Renewer of the Church who truly brought things ad fontes, or back to the basics in regards to making the Scriptures the foundational norm for church practice and tradition. Martin Luther's plea for a General Church Council to address these abuses fell flat for most of his life, but his suggestions of reform found eager listeners in the churches of Northern Germany, Scandinavia and parts of southern Germany. The Council of Trent solidified Roman Catholic teachings largely as a response to the clerical abuses that Luther, Zwingli, Conrad Grebel, Calvin and others pointed out and also as a refutation of the teachings that Luther, Grebel and Calvin promulgated as a result.
Martin Luther's teachings, coupled with his voracious writing and Biblical insights, sped across Europe with the help of the relatively new printing press. When his works were translated from Ecclesiastical Latin into German, he held a larger public audience. Martin Luther translated the Bible into German and thus made his Saxon dialect into the standard German language. A University professor, Luther encouraged education of the laity, especially in reading the Bible and the Small Catechism. He was a human being and his writings inevitably reflected that not only was he a dedicated Christian, but also a man tormented by his own doubts and frustrations. He had prejudices common to the German people of his day and age ( which were really rather similar to the prejudices of other Western Europeans of the sixteenth century) and he'd write them, becoming more strident as his health worsened and as he aged.
Martin Luther was a saint and sinner all at once. He wanted his people to be called Evangelical Catholics, rather than Lutherans, but in the end, he had to accept the moniker that his opponents fastened on those who followed teachings he considered to be foundationally Christian, found in the teachings of the Gospels and the Early Church Fathers. These teachings were not " Lutheran" in the sense that Luther pulled them out of thin air as his own, but teachings gleaned from a lifetime of careful and diligent study. He was a sinner in that he could be vicious to his opponents ( as well as those who sought to be his friends) and many times, his zeal led him to write intemperate things. He was a great man, but a man still, like all of us, utterly dependent on the grace of God alone.