backslider vs reversionist

backslider and reversionist both are nouns.

Word	Noun	Adjective	Verb	Adverb
backslider	Yes	No	No	No
reversionist	Yes	No	No	No

As nouns, backslider and reversionist are synonyms defined as:

backslider and reversionist: someone who lapses into previous undesirable patterns of behavior

Other synonyms of backslider include recidivist.

backslider (noun)	reversionist (noun)
someone who lapses into previous undesirable patterns of behavior	someone who lapses into previous undesirable patterns of behavior