The phrase "implacable enemy" refers to someone who is unable or unwilling to forgive or make amends, and is determined to oppose or harm another person no matter what. Full definition
A fictional account of the extraordinary story of two implacable enemies in Northern Ireland - firebrand Democratic Unionist Party leader Paisley (Timothy Spall) and Sinn Fein politician Martin McGuinness (Colm Meaney)- who are forced to take a short journey together in which they will take the biggest leap of faith and change the course of history. (firstshowing.net)
It is abundantly clear from the New Testament record of Paul's life that the Jewish religion, in which he himself was nurtured, proved as implacable an enemy to the new Faith as paganism itself. (religion-online.org)
In biblical Hebrew, yeshu'ah is a distinctly here - and - now word: we are up to our neck in trouble, surrounded by implacable enemies, and we trust in, or implore, God to get us out. (firstthings.com)