If you say that someone is implacable, you mean that they have very strong feelings of hostility or disapproval which nobody can change.
例句
...the threat of invasion by a ruthless and implacable enemy...殘暴無情的敵人發出的侵略威脅The move has won the implacable opposition of many economists.該提案遭到了許多經濟學家的堅決反對。