stickler

/ˈstɪklər/
noun
  1. A person who insists on strict adherence to rules, details, or standards.
    • As a stickler for fairness, the referee made sure every rule was followed.
    • My boss is a stickler for punctuality and hates it when anyone is late.
    • She is a stickler about grammar and corrects every mistake she sees.
Antonyms