How many letters does the top answer for “action intended to nullify the effects of some previous action” have?

The most common answer is counteraction (13 letters).

Crossword clue: action intended to nullify the effects of some previous action

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

counteraction 13 letters wn-def

action intended to nullify the effects of some previous action

neutralisation 14 letters wn-def

action intended to nullify the effects of some previous action