Which word best represents an action that is characterized as deceitful yet flattering?

The word "unctuously" is the best choice because it specifically conveys a sense of insincerity wrapped in smooth or ingratiating flattery. When someone acts unctuously, they often come across as overly flattering in a way that seems disingenuous, suggesting a hidden agenda or deceitful intent. This term carries connotations of slickness or a false sense of charm, making it suitable to describe actions that are both deceitful and seemingly flattering at the same time.

The other options do not capture this dual nature effectively. "Nobly" implies an honorable and virtuous action, while "innocently" suggests purity and a lack of malevolence. On the other hand, "clearly" denotes transparency and straightforwardness, lacking any hint of deceit or flattery. Thus, while those words have their own meanings, they do not align with the specific characterization of deceitful yet flattering behavior that "unctuously" does.