two-faced

This term carries a strong negative charge, describing a specific type of betrayal where a person maintains a facade of friendship or loyalty while actively undermining the target. It evokes the image of a Janus-like figure, suggesting a calculated duality of personality rather than simple indecisiveness.

Because it describes a character trait, it is primarily used in interpersonal contexts and social critiques. It is more severe than being "tactful" or "diplomatic," as it implies a malicious intent to deceive for personal gain or social leverage.