Henry had those who opposed his imposition of Roman Catholicism without the pope executed in various horrible ways (doctrinally, he changed nothing). Mary had those who opposed her either religiously or politically executed in similar fashion. Elizabeth was much more poilitic, until Pope Pius V excommunicated her, which required all who adhered to his leadership to actively seek to remove her from the throne. This came after Mary Queen of Scots had waged war on her cousin, at the pope's instigation.