Question: Which Roman emperor was regarded as the third of the Five Good Emperors but is know for killing Saint Thamel?

Context paragraphs:
Thamel (martyr): Saint Thamel and companions (died 125 AD) are a group of 2nd century Christian martyrs. Thamel was a priest for a pagan god who was converted to Christianity.  He was killed with his sister during the persecutions of Christians under the Roman emperor Hadrian.

Concordat of Worms: The Concordat of Worms (Latin: "Concordatum Wormatiense" ), sometimes called the Pactum Calixtinum by papal historians, was an agreement between Pope Calixtus II and Holy Roman Emperor Henry V on September 23, 1122, near the city of Worms.  It brought to an end the first phase of the power struggle between the Papacy and the Holy Roman Emperors and has been interpreted as containing within itself the germ of nation-based sovereignty that would one day be confirmed in the Treaty of Westphalia (1648).  In part this was an unforeseen result of strategic maneuvering between the Church and the European sovereigns over political control within their domains.  The King was recognised as having the right to invest bishops with secular authority ("by the lance") in the territories they governed, but not with sacred authority ("by ring and staff").  The result was that bishops owed allegiance in worldly matters both to the pope and to the king, for they were obliged to affirm the right of the sovereign to call upon them for military support, under his oath of fealty.  Previous Holy Roman Emperors had thought it their right, granted by God, to name Church officials within their territories (such as bishops) and to confirm the Papal election (and, at times of extraordinary urgency, actually name popes).  In fact, the Emperors had been heavily relying on bishops for their secular administration, as they were not hereditary or quasi-hereditary nobility with family interests.  A more immediate result of the Investiture struggle identified a proprietary right that adhered to sovereign territory, recognising the right of kings to income from the territory of a vacant diocese and a basis for justifiable taxation.  These rights lay outside feudalism, which defined authority in a hierarchy of personal relations, with only a loose relation to territory.  The pope emerged as a figure above and out of the direct control of the Holy Roman Emperor.

Heroes of History: Heroes of History: A Brief History of Civilization from Ancient Times to the Dawn of the Modern Age is a book by Will Durant, published in 2001 and was written as a summary of Will and Ariel Durant's "The Story of Civilization".  It describes important personalities and events in History.  These 'Heroes' include Laozi, Muhammad, Kung fu Tze, The Buddha, Mohandas K. Gandhi, Akhenaton, Jewish prophets, Solon, Pericles, Euripides, Socrates, Julius Caesar, Augustus, The Five Good Emperors, Jesus Christ, Lorenzo de Medici, Leonardo da Vinci, Martin Luther, William Shakespeare and Sir Francis Bacon, among others.  Originally planned as a series of audio lectures, "Heroes of History" was supposed to have twenty-three chapters, but Durant completed only twenty one before his death in 1981.

Antoninus Pius: Antoninus Pius (Latin: "Titus Aelius Hadrianus Antoninus Augustus Pius" ; 19 September 867 March 161), also known as Antoninus, was Roman emperor from 138 to 161.  He was one of the Five Good Emperors in the Nerva–Antonine dynasty and the Aurelii.

Constantine the Great: Constantine the Great (Latin: "Flavius Valerius Aurelius Constantinus Augustus" ; Greek: Κωνσταντῖνος ὁ Μέγας ; 27 February 272 AD – 22 May 337 AD), also known as Constantine I or Saint Constantine (in the Orthodox Church as Saint Constantine the Great, Equal-to-the-Apostles), was a Roman Emperor of Illyrian-Greek origin from 306 to 337 AD.  He was the son of Flavius Valerius Constantius, a Roman Army officer, and his consort Helena.  His father became "Caesar", the deputy emperor in the west, in 293 AD.  Constantine was sent east, where he rose through the ranks to become a military tribune under Emperors Diocletian and Galerius.  In 305, Constantius raised himself to the rank of "Augustus", senior western emperor, and Constantine was recalled west to campaign under his father in Britannia (Britain).  Constantine was acclaimed as emperor by the army at Eboracum (modern-day York) after his father's death in 306 AD, and he emerged victorious in a series of civil wars against Emperors Maxentius and Licinius to become sole ruler of both west and east by 324 AD.

Roman emperor: The Roman emperor was the ruler of the Roman Empire during the imperial period (starting in 27 BC).  The emperors used a variety of different titles throughout history.  Often when a given Roman is described as becoming "emperor" in English, it reflects his taking of the title "Augustus" or "Caesar".  Another title often used was "imperator", originally a military honorific.  Early Emperors also used the title "princeps" (first citizen).  Emperors frequently amassed republican titles, notably "Princeps senatus", "Consul" and "Pontifex Maximus".

Marcus Aurelius: Marcus Aurelius ( ; Latin: "Marcus Aurelius Antoninus Augustus" ; 26 April 121 – 17 March 180 AD) was Roman emperor from , ruling jointly with Lucius Verus until Verus' death in 169 and jointly with his son, Commodus, from 177.  He was the last of the so-called Five Good Emperors.

History of the Roman Empire: The history of the Roman Empire covers the history of Ancient Rome from the fall of the Roman Republic in 27 BC until the abdication of the last Western emperor in 476 AD.  Rome had begun expanding shortly after the founding of the Republic in the 6th century BC, though it did not expand outside of the Italian Peninsula until the 3rd century BC.  Civil war engulfed the Roman state in the mid 1st century BC, first between Julius Caesar and Pompey, and finally between Octavian and Mark Antony.  Antony was defeated at the Battle of Actium in 31 BC.  In 27 BC the Senate and People of Rome made Octavian "imperator" ("commander") thus beginning the Principate, the first epoch of Roman imperial history usually dated from 27 BC to 284 AD; they later awarded him the name Augustus, "the venerated".  The success of Augustus in establishing principles of dynastic succession was limited by his outliving a number of talented potential heirs: the Julio-Claudian dynasty lasted for four more emperors—Tiberius, Caligula, Claudius, and Nero—before it yielded in 69 AD to the strife-torn Year of Four Emperors, from which Vespasian emerged as victor.  Vespasian became the founder of the brief Flavian dynasty, to be followed by the Nerva–Antonine dynasty which produced the "Five Good Emperors": Nerva, Trajan, Hadrian, Antoninus Pius and the philosophically inclined Marcus Aurelius.  In the view of the Greek historian Dio Cassius, a contemporary observer, the accession of the emperor Commodus in 180 AD marked the descent "from a kingdom of gold to one of rust and iron"—a famous comment which has led some historians, notably Edward Gibbon, to take Commodus' reign as the beginning of the decline of the Roman Empire.

Hadrian: Hadrian ( ; Latin: "Publius Aelius Hadrianus Augustus" ; 24 January 76 – 10 July 138) was Roman emperor from 117 to 138.  He is known for building Hadrian's Wall, which marked the northern limit of Britannia.  He also rebuilt the Pantheon and constructed the Temple of Venus and Roma.  Philhellene in most of his tastes, he is considered by some to have been a humanist, and he is regarded as the third of the Five Good Emperors.

Trajan: Trajan ( ; Latin: "Imperator Caesar Nerva Traianus Divi Nervae filius Augustus" ; 18 September 538August 117 AD) was Roman emperor from 98 to 117AD.  Officially declared by the Senate "optimus princeps" ("the best ruler"), Trajan is remembered as a successful soldier-emperor who presided over the greatest military expansion in Roman history, leading the empire to attain its maximum territorial extent by the time of his death.  He is also known for his philanthropic rule, overseeing extensive public building programs and implementing social welfare policies, which earned him his enduring reputation as the second of the Five Good Emperors who presided over an era of peace and prosperity in the Mediterranean world.

Supporting paragraphs: Thamel (martyr) Hadrian
Answer: Hadrian