what can we call someone who gives false promise to someone repeatedly but intentionally break the promise?

someone promised me to help solve my problem but he did not help me. he promised me again but still intentionally make excuses. or someone borrowed money from me and gave me many dates to repay but intentionally he gave me so many excuses every time. is there any idioms or phrases to explain their intentional dodgy behaviour?


Solution 1:

Perfidious - :  of, relating to, or characterized by perfidy

perfidious