IPA: /ˌmælɪˈfækʃən/
KK: /mælɪˈfækʃən/
An act that is harmful or evil, often referring to a crime or wrongdoing.
The villain was punished for his malefaction against the innocent.
Malefaction is formed from "male" (from Latin *male*, meaning badly or ill) and "factio" (from Latin *facere*, meaning to do or make). The word refers to the act of doing something bad or evil.
Think of 'male' meaning badly and 'factio' meaning to do — this helps you remember that malefaction refers to the act of doing something bad.