Which word best describes a clever act of manipulation?

The term "cunning" is particularly well-suited to describe a clever act of manipulation because it conveys both intelligence and scheming intent. Someone who is cunning devises clever strategies, often with an underhanded motive, to achieve their goals. This synonym relates directly to the idea of manipulation, suggesting a degree of craftiness and shrewdness that is essential for executing such acts successfully.

In contrast, "adequate" refers to something that is sufficient or satisfactory, but does not imply any cleverness or manipulation. "Transparent" suggests openness and clarity, which directly opposes the essence of manipulation, where actions are often concealed or deceptive. Lastly, "optimistic" conveys a hopeful or positive outlook, which is unrelated to the concept of manipulation or clever acts, focusing instead on the emotional state rather than the strategic or cunning nature of actions. Thus, "cunning" is the most fitting choice for describing clever manipulation.