표리부동
表裏不同 · the outside and inside differ
Two-faced; saying one thing, meaning another.
When to useCriticizing someone who's nice to your face only.
Examples
앞에선 칭찬하고 뒤에선 흉보다니, 표리부동하네.
Praising you to your face and gossiping behind your back — so two-faced.