How many letters does the top answer for “a change for the worse” have?

The most common answer is deformation (11 letters).

Crossword clue: a change for the worse

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

deformation 11 letters wn-def

a change for the worse

distortion 10 letters wn-def

a change for the worse

the occurrence of a change for the worse 67% similar → damage, impairment