Final answer:
Thomas Becket is the individual who defied Henry Plantagenet (also known as King Henry II of England) and was later canonized as a saint by the Catholic Church following his martyrdom. The conflict arose from Henry II's attempts to reform the clergy's privileges, which Becket opposed as the Archbishop of Canterbury.
Step-by-step explanation:
The individual who defied Henry Plantagenet and became a saint is Thomas Becket, the Archbishop of Canterbury during the reign of King Henry II of England. This historical opposition occurred during a time of significant religious and political upheaval in England. When Henry II sought to reform the powers of the clergy and their judicial privileges, Becket resisted, leading to a long-standing conflict between the crown and the church. This conflict ultimately led to Becket's martyrdom and subsequent canonization as a saint by the Catholic Church.
While the information provided discusses several historical figures named Henry in the context of religious strife and reform, including Henry VIII's break with the Catholic Church and the creation of the Church of England, it does not directly answer the student's question about Henry Plantagenet. Henry Plantagenet commonly refers to King Henry II. However, historical records indicate that it was Thomas Becket who became a saint after defying Henry II's efforts to reduce the power of the church.