Very strict or harsh
Rules, at times, can be very strict and harsh.
A parent
severe
Rigorous or stringent.
He was a very strict and harsh ruler
Another word for very strict or harsh is stern.
Harsh
Severe
Crossword puzzles may include a synonym of harsh, and it may be severe.
The guide words for "harsh" could be "hard" and "strict."
Severe.
Lamented or sternly