How many letters does the top answer for “someone who lapses into previous undesirable patterns of behavior” have?

The most common answer is backslider (10 letters).

Crossword clue: someone who lapses into previous undesirable patterns of behavior

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

backslider 10 letters wn-def

someone who lapses into previous undesirable patterns of behavior

recidivist 10 letters wn-def

someone who lapses into previous undesirable patterns of behavior