grueler
/ˈɡruːələr/
noun
- A person or thing that subjects someone to very hard, tiring work or effort.
- She's a grueler when it comes to deadlines, expecting perfect work under tight time limits.
- This marathon is known as a grueler because of the steep hills and hot weather.
- The new coach is a real grueler, making the team run laps every morning.
Synonyms