Final answer:
Queen Elizabeth I was the monarch who got excommunicated in 1570 and faced religious and political challenges during her reign, including the threat from Mary, Queen of Scots.
Step-by-step explanation:
The individual who was excommunicated in 1570 and against whom the church sanctioned efforts to dethrone was Queen Elizabeth I. During her reign, Elizabeth faced challenges from within the Church of England, particularly from the Puritans who wanted to purify the church of Catholic influences.
Elizabeth's moderate stance in religion and her establishment of the Anglican Church, which retained some Catholic traditions while adopting Protestant doctrines, created religious stability but also dissent. Furthermore, her cousin Mary, Queen of Scots—a staunch Catholic—sought to claim Elizabeth's throne, which ultimately led to Mary's execution for treason in 1587.