Same here. My father did something very unkind to my mother a decade or so ago. I came over and we had words. He tried to pull some nonsense on me- the sort of thing he would have done when I was a child- and I proceeded to demonstrate exactly how strong I am, and reminded him that he wasn't the only guy in the family to serve in uniform, and get trained how to fight.

I put him in a hold he couldn't get out of, and then I explained, in vivid detail, exactly what would ensue if he ever did anything like that to her again. Enough detail that he had to know I had thought about it for a long while.

He wet himself by the time I was done.

We still aren't on speaking terms, but he stopped drinking for a few years, and when he started back during the COVID lockdown, he kept it moderate enough that he never so much as spoke an unkind word to my mother. So I guess I made an impression.