perfidious
adjective literary uk/pəˈfɪd.i.əs/ us/pɚˈfɪd.i.əs/
背信弃义的;不忠贞的
unable to be trusted, or showing no loyalty
She described the new criminal bill as a perfidious attack on democracy. 她称新的刑法提案是对民主的肆意践踏。
Synonym: treacherous