What term describes an adversary who instills fear to achieve political or ideological goals?

The term that describes an adversary who instills fear to achieve political or ideological goals is "terrorists." Terrorism is characterized by the use of violence or threats to intimidate or coerce societies or governments. This tactic is often employed by individuals or groups who seek to advance specific political objectives or ideological agendas. By creating a climate of fear, terrorists aim to influence public perception, provoke reactions from authorities, and push their agenda onto the national or international stage.

The other terms listed do not encapsulate this specific behavior and its wider implications. Criminals may engage in illegal activities for personal gain but do not typically operate with the aim of instilling fear for political or ideological purposes. Foreign intelligence agents are primarily concerned with gathering information and may use subterfuge but do not primarily operate through the instillation of fear as a tactic. Insiders usually refer to individuals who have authorized access to sensitive information or areas and pose a risk from within an organization, but they are not specifically defined by the use of fear to achieve goals in the same way that terrorists are.