oathbreaker
A total cheat who promises to do something big but then runs away when it gets tough. They just care about their own skin and don’t give a damn about the people they swore to protect.
He took the oath and then ran when the crowd got angry.
She promised to fix the country but then took all the money and left everyone behind.
He swore to protect the country but then took a helicopter and flew away while everyone got hurt.