This is a post to honour a brave man of God most have never heard of called Michael Servetus 1511-1553.
The genius of Michael Servetus extends to many fields of human endeavor: jurisprudence, mathematics, geography, astrology, philosophy, medicine, theology, and biblical criticism.
He was murdered by John Calvin because Michael Servetus did not agree with the trinitarian doctrine.
The below text is from Sir Anthony Buzzard book The Doctrine of the Trinity pages 154-158.
A remarkable example of how Christian leadership sometimes responds when its age-old doctrine of the Trinity is threatened by the idea that God is a single person, is shown by the reaction of one highly regarded leader of the Protestant Reformation, John Calvin. The unfortunate victim of Calvin’s cruelty was the anti-Trinitarian, Michael Servetus.
Servetus, educated in the Catholic religion, trained in civil law and subsequently in medicine, was appalled at the pomp and adoration given to the Pontiff in Rome. After coming under the influence of the early Reformation, Servetus continued his energetic study of the Bible and became the first Protestant to attack the doctrine of the Trinity.
His writings leave little doubt that he was exceptionally well-educated, schooled in both Hebrew and Greek. He declared in a somewhat emotive, even abrasive manner that the Catholic dogma of the three divine Persons in the Godhead was a construct of the imagination, a monster compounded of incongruous parts, metaphysical gods, and philosophical abstracts.  The accusation attracted the notice of Calvin who responded that Servetus “deserved to have his bowels ripped out, and to be torn to pieces.” 
Ironically, although Servetus was largely sympathetic to the Protestant cause, he soon found Protestant Germany and Switzerland off-limits for him. He was, however, able to find a home in the palace of a Roman Catholic Archbishop in France who was an admirer of learned men. By then Servetus had become a skilled physician and the first one to publish an account of the passage of the blood from the right ventricle to the left auricle of the heart. The diversity of his accomplishments showed him to be intellectually the equal of other reformers.
His continued correspondence with Calvin on the Trinitarian issue did not, however, ingratiate him with the constituted authority of Geneva, where Calvin had come virtually to control a powerful theocratic system. He told Calvin, “Your Gospel is without the one God, without true faith, without good works.
Instead of the one God you have a three-headed Cerberus”  (the mythological Greek three-headed dog who guarded the gates to Hell). He further stated to Calvin, “instead of true faith you have a fatal delusion; and good works you say are empty show.”  These words would certainly not qualify Servetus for the diplomatic corps. But we should not doubt his integrity or the courage of his convictions.
Calvin, true to the spirit of Constantine, vowed to kill him when it was in his power to do so. Servetus determined, however, to publish one more work, designed to restore Christianity to its original purity and to free it from the errors which had polluted the faith. Calvin obtained a copy of Servetus’ finished work attacking the Trinitarian doctrine. He then proceeded through an intermediary to have the Catholic Church arrest Servetus. During his incarceration he was treated with respect and after three days was given a key by the jailer for a walk in the gardens.
He escaped and walked to freedom; but it turned out to be a death walk.
His freedom was short-lived. Determined to go to Naples in Italy to continue his practice as a physician, he made the unfortunate decision to travel via Geneva. This was Calvin’s territory. Ruling with almost absolute power, he had established an ecclesiastical theocracy. Servetus could no doubt reason that if caught, his treatment from fellow Protestants might be more merciful than if he fell into the hands of the Catholic authorities. After his escape, the Catholic Church had tried him in absentia and sentenced him ”to be drawn in a dung cart to the place of punishment and there to be burned alive (tout vif) by a slow fire, with his books.” 
Tragically, Servetus did not reckon with the character of his Protestant enemy who had said, “if he comes and if any regard be had to my authority I shall not suffer him to escape with life.”  Calvin later admitted: “I do not conceal that through my exertions, and by my council he was thrown into prison: 
Calvin would have better served his modern apologists had he not written an account of his dealings with Servetus. But it is not uncommon for followers of any leader to turn a blind eye and remove from public view the most objectionable aspects of their hero’s conduct, without strict regard for the facts.
Servetus experienced the full force of the ruthless Calvin.
After suffering cruel privation and humiliation, he was bound to the stake with an iron chain, his last book fastened to his thigh. After he had begged his executioner not to torment long, the fire was applied to a scanty pile of green oak branches. He lingered a long time in torment, crying out with a piercing voice, “Jesus, Son of the eternal God, have mercy upon me!” At last some of the spectators, out of compassion, threw faggots [burning sticks] upon him to put an end to his misery. 
Thus ended the life of a brilliant man whose studies of the Bible put him in opposition to a powerful 16th-century Protestant reformer. Despite any historical disagreement over the strengths and weaknesses of the two antagonists in this tragic drama, the plain fact remains that Servetus was burned at the stake for his opposition to a religious doctrine – the Trinity. He suffered a cruel death for daring to publish his honest well-studied disagreement with hallowed tradition whose supporter felt threatened. Time has not succeeded in erasing this fearful blot from established Christianity’s record.
It would be wrong to believe that religious or secular opposition to belief in a single-person Deity is confined to an ancient past. Through one means or another, covert or overt, the biblical concept of a Deity of one person, the “one God, the Father,” of Paul’s creed (1 Corinthians 8:6), has been hidden under a blanket of contradictory words, phrases and suppressed discussion.
The violence with which the doctrine of the Trinity has been defended casts a pall of suspicion over it. Something seems desperately wrong with a teaching that has precipitated such tragic and bloody episodes in church history. The dogma which even its proponents say cannot be explained and one which makes little sense to the rational mind was the product of Greek thinking. It was at odds with the Hebraic theology in which Jesus and the Apostles were nurtured. The God of Moses, Isaiah, Jesus, and the Apostles was one person, the Father. One cannot be made equal to two or three. All that can be done with one is to fractionalize it.
Divide it into smaller segments and it is no longer one. Expand it, and in spite of prodigious mental gymnastics on the part of Trinitarians, it cannot be made into two or three and still remain one. (This is not to say, of course, that God may not appoint agents to extend His influence and exercise His authority. But this is not an ontological but a fiduciary relationship.) God will not submit to fractionalization or division.
When Christianity took its formal initial step forcing a division of God into two (Father and Son), it fragmented itself, not God. So the Christian world remains to this day; not unified as Christ prayed, but segmented into conflicting denominations. This fact should cause us to ponder the question: If Christ prayed that his Church would be one (John 17:20, 21), was that prayer not answered? Is it possible that today’s divided and confused religious community is in fact Christian in name only? Could its primary creed be a deviation from the Bible it loudly claims as its standard?
If we lay aside the imaginative speculations of Greek philosophers and theologians; if we omit argument from inference in our search for the true God and the real Jesus, and rely on Scripture’s plain creedal declarations, the Bible reveals that Jesus was the Messiah, Son of God. This is the New Testament’s central “dogma.” This is the creed of the earliest Christians, and there is no need to alter their perception of the Savior by presenting him as a preexistent super-angel or as the eternal God who became man.
It is reasonable to account for the shift in thinking which now makes it hard for Bible readers to distinguish the legacy of tradition from the original teaching of Jesus and the Apostles. A Christian in search of truth will have nothing to fear from the facts.
1 General Repository and Review, ed. Andrews Norton (Cambridge, MA: William Hilliard, Oct., 1813), 4:37.
3 Ibid., 47.
5 Ibid., 56.
6 Ibid., 48.
7 Ibid., 58.
8 Ibid., 72.
The following download is a time overview of Michael Servetus life.