Hypocritical.
insincere, liar, untrustworthy come to mind.
An insincere person should not be trusted
The word 'glib' means fluent but insincere.
An insincere apology is no better than no apology. I noticed that she was insincere when she said the shirt that was too small for me looked good.
Some synonyms of the word "insincere" are ambidextrous, backhanded, and deceitful. Other synonyms include deceptive, devious, disingenuous, and dissembling.
Lip service
deceitful, deceptive, insincere
Hypocritical or lacking honesty.
insincere
The negative of "sincere" is "insincere," which describes a lack of honesty or genuineness in feelings or expressions. An insincere person may say one thing while meaning another, often leading to distrust or misunderstanding. This term is often associated with deceitfulness or superficiality in communication.
what is another word for person
It can depending on the person and it also depends if you are the one being unfaithful/ insincere or if your spouse is.