noun
Broadly used as in English: physical movement, activity, or the events in a story. Common in compounds like アクション映画 (action movie).
彼はアクション映画が大好きだ。
He loves action movies.
このゲームはアクションがとても速い。
The action in this game is very fast.
行動 is the native Japanese word for 'action' or 'behavior', often used in more formal or abstract contexts, while アクション is a loanword with a slightly more dynamic, entertainment, or physical nuance.
Loanword from English 'action'.