a force to be reckoned with - A person or thing that is really strong and can’t be messed

A person or thing that is really strong and can’t be messed with. You’d be crazy to mess with them.

My brother is a force to be reckoned with. He once beat up a kid for stealing my snack.

My friend’s new boss is a force to be reckoned with. He once yelled at the whole office for five minutes straight.

My coach is a force to be reckoned with. He once made me run laps for not tying my shoes.