From Wikipedia, Luther taught that salvation and, consequently, eternal life are not earned by good deeds but are received only as the free gift of God's grace through the believer's faith in Jesus Christ as redeemer from sin. His theology challenged the authority and office of the pope by teaching that the Bible is the only source of divinely revealed knowledge, and opposed sacerdotalism by considering all baptized Christians to be a holy priesthood. Luther insisted on Christian or Evangelical (German: evangelisch) as the only acceptable names for individuals who professed Christ.
His translation of the Bible into the German vernacular (instead of Latin) made it more accessible to the laity, an event that had a tremendous impact on both the church and German culture. It fostered the development of a standard version of the German language, added several principles to the art of translation, and influenced the writing of an English translation, the Tyndale Bible. His hymns influenced the development of singing in Protestant churches. His marriage to Katharina von Bora, a former nun, set a model for the practice of clerical marriage, allowing Protestant clergy to marry.
In two of his later works, Luther expressed antagonistic, violent views towards Jews and called for the burnings of their synagogues and their deaths. His rhetoric was not directed at Jews alone but also towards Roman Catholics, Anabaptists, and nontrinitarian Christians.
In view of these things, Martin Luther had profound impact on Protestant Christianity, and I think all his position originally established what is orthodox teaching in Christianity, as opposed to that in the Roman Catholic Church which was all else known of Christianity in that area in that time. His intolerance late in his life may be connected to tragedies he experienced, such as the death of his daughter in her childhood. It seemed to lead to obsession with death. He did error in this direction, yet in the setting we can identify him with humanity, just as David, however saintly we are we can seriously error tragically, because we are still human with the fallen nature remaining in this life.
