IPA: /ˈriːkər/
KK: /ˈrikər/
A person who causes harm or damage, often as a form of revenge or punishment.
The wreaker of havoc left the town in ruins after the storm.
Wreaker → It is formed from "wreak" (from Old English *wrecan*, meaning to take vengeance or to inflict) and "-er" (meaning a person who). A wreaker is a person who inflicts or causes something, often in a destructive manner.
Think of someone who 'inflicts' ('wreak') something, and the '-er' just means a person. A wreaker is someone who causes destruction or harm.