Two-faced and Undutiful

Two-faced adjective - Not being or expressing what one appears to be or express.

Undutiful and two-faced are semantically related In some cases you can use "Undutiful" instead an adjective phrase "Two-faced".

Undutiful adjective - Lacking due respect or dutifulness.

Two-faced and undutiful are semantically related in disloyal topic. Sometimes you can use "Two-faced" instead an adjective "Undutiful", if it concerns topics such as treasonous.