From Longman Dictionary of Contemporary Englishbe a hard/stern/tough taskmasterbe a hard/stern/tough taskmasterFORCE somebody TO DO somethingto force people to work very hard → taskmaster
Examples from the Corpus
be a hard/stern/tough taskmaster• True to his word, he schooled her in horsemanship and was a hard taskmaster.• She was a hard taskmaster but a considerably fairer one than la Belle Ethel.• If self-employment is any guide, the dejobbed worker is likely to be a stern taskmaster. 