To rule with an iron fist means to rule in a stern manner.
To control a group of people very sternly.
Having complete power over everything.
1. The king ruled with an iron fist and often intimidated members of the royal family.
2. The boss at my company rules with an iron fist and I get so jumpy when I’m around him.
3. My mom rules with an iron fist in our home.
4. Our President rules our country with an iron fist.
big stick, control, firm hand, grip, hard line, heavy hand, high hand, iron boot, iron rule, jackboot, mailed fist, stern, strong hand, tight grasp, tight hand, tight rein, tight ship