
perfide
perfidious
Malicious or deceitful in a treacherous, insidious, and vile way. It describes an action or plan that aims to abuse trust and deliberately cause harm.
Es war ein perfider Plan, ihre Freundschaft nur vorzutäuschen, um an die vertraulichen Informationen zu gelangen.
It was a perfidious plan to merely pretend to be her friend in order to get the confidential information.