backslider vs wrongdoer

backslider and wrongdoer both are nouns.

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

As nouns, wrongdoer is a hypernym of backslider; that is, wrongdoer is a word with a broader meaning than backslider:

backslider: someone who lapses into previous undesirable patterns of behavior
wrongdoer: a person who transgresses moral or civil law

Other hypernyms of backslider include offender.

backslider (noun)	wrongdoer (noun)
someone who lapses into previous undesirable patterns of behavior	a person who transgresses moral or civil law