backslider

A recidivist; one who backslides, especially in a religious sense; an apostate.

She married him thinking to change his ways, and for a while he got religion, but he was ever a backslider; she soon began finding bottles stashed about the house.

At night the Red Elephant Tusk boomed and groaned among the hills, and the faithful waked and said: ‘The God of Things as They Are matures revenge against the backsliders.’

One who will not do his work or shoulder his responsibilities.