Which word would describe someone or something that creates disturbance or unrest?

The word that effectively describes someone or something that creates disturbance or unrest is "agitate." This term implies causing a stir, provoking emotional or physical responses, or inciting reactions that lead to unrest. In various contexts, such as political discourse or social movements, to agitate means to actively challenge the status quo, making it clear that disturbance is at the core of its meaning.

While other words like "pacify," "comfort," and "quiet" suggest a sense of calmness or the act of reducing disturbance, "agitate" distinctly conveys the notion of stirring up or causing turmoil, making it the best choice for describing something that disrupts peace or stability.