What would best describe actions taken that serve to undermine a system or authority?

The term that best describes actions taken to undermine a system or authority is "subversive." Subversive actions are intended to disrupt or challenge the established norms, structures, or governance within a system. When individuals or groups engage in subversive behavior, they often seek to bring about change by dismantling, weakening, or questioning the legitimacy of the existing authority. This can manifest in various forms, such as through protests, dissenting propaganda, or covert actions aimed at fostering dissent among those within the system.

In contrast, supportive actions are those that reinforce or back a system or authority, while transparent actions focus on openness and honesty, facilitating trust and accountability within a system. Compliance refers to adherence to rules, regulations, or directives, which is contrary to undermining any established authority. Therefore, subversive clearly encapsulates the efforts aimed at undermining authority, making it the most appropriate choice.