IPA: /ˈmælɪˌfæktər/
KK: /mælɪˌfæktər/
A person who does bad things or commits crimes.
The police arrested the malefactor after a long investigation.
Malefactor → It is formed from "male" (from Latin *malus*, meaning bad or evil) and "facere" (meaning to do or make). The word "malefactor" refers to someone who does evil or commits a crime.
Think of someone who does something 'bad' ('male') — that's why a malefactor is a person who commits evil acts.