The Apostle John was not a martyr, although the Romans attempted to kill him. Paul was beheaded in Rome about the year 64-67 for being a Christian.
Both Peter and Paul were martyred in Rome.
Yes, he was martyred for being a Christian.
John was the forerunner of Our Lord, preached a baptism of repentance and was martyred for his religious beliefs.
Nero.
All the Apostles were martyred except John, who died of old age, and the Apostle Paul was beheaded by Nero in 67-68AD [Roman and Hebrew calendars do not coincide].
The beheaded saints typically refer to saints who were martyred by beheading for their religious beliefs. Saint John the Baptist and Saint Paul are among the well-known beheaded saints in Christian tradition.
Vincent de Paul was not martyred. He died of natural causes.
St. Peter was martyred in Rome around 64-67 AD, where he was crucified upside-down at his own request. St. Paul was also martyred in Rome around 64-67 AD, where he was beheaded due to his beliefs as a Christian. Both saints were persecuted during the reign of Emperor Nero.
St. Justin was martyred for his Christian beliefs and refusal to participate in traditional Roman religious practices. He openly taught and defended his faith, which led to his arrest and subsequent execution. His commitment to his beliefs and willingness to die rather than renounce them made him a martyr.
John
Saint Lorenzo Ruiz became a saint by being martyred for his faith in Japan in 1637. He endured torture with great courage and refused to renounce his Catholic beliefs, ultimately sacrificing his life for his faith. He was beatified by Pope John Paul II in 1981 and later canonized as a saint in 1987.
Vincent de Paul was not martyred. He died of natural causes.