Yeah, you are asking the question, about 10 years too late. What can you do about a kid fighting with their parents? That's way too late to ask the question. You need to ask that when they are 2 years old.
The kids that are biting and kicking, are doing that because over the last dozen years of their life, they learned their parents would not fight back.
I remember my watching my father get smacked by a nephew, and that only happened once.... one time...
"well he's two! you can't punish him when he's two! It's cute!"
Bull crap..... TWO is when you need to teach them what they can and can't do. Because if you think you'll wait until he's 13 to tell him kick and slapping parents is not good, it's way way too late.
Again, I've seen this first hand. I had a relative who didn't do that with his DAUGHTER... and she came over while I was there, and she started breaking stuff and screaming and yelling, and abusing his wife, and he just sat there, and she just glared at him, and I could tell instantly that he had never stood up to her, and both she, and him, knew that he wasn't going to stop her at all.
What can you do about that? Crap, there is nothing you can do about that. The deed is done. The bad seed has been planted in wrong fields for a decade or more, and now you are just going to reap the whirl wind (to take a Biblical phrase).
The only solution you have at that point, is to disown your kids. Which is exactly what these parents absolutely won't do, which is why their kids abuse them.
Which, by the way... I would have no problem with.
See the problem is kids know you won't do jack, that's why you have no other options.
I have always known personally.... always knew this.... if I ever was caught by my father abusing my mother, he would disown me, write me out of the will, and cut off all communication with me. I could argue with my father now and then, but I *NEVER* had issue with my mother, because I knew he'd go WW3 on me. That's why I never caused a problem.
It's when you know the other person will fight back with brutal force, that you don't cause problems. It's the kids who know their parents won't do jack squat, that treat their parents like trash.
By the way, this is why women generally make terrible parents. Women want to just "talk it out" and such. My father had a paddle. Wooden paddle. If I acted up horrifically, he caused some horrific pain. That's why I treat him with respect and honor. He taught me right from wrong.
Women don't do that. "now how many times I have I told you Timmy".... yeah... you just told him. That's like nothing. He knows he can do whatever he wants, and all you'll do is "blaw blaw blaw.... blaw blaw!! Blaw.... sigh... blaw blaw blaw".
So what do you do once your kid is already abusing you....?
First, I'd have a paddle, and paddle his butt. Then I'd take away everything.... as in everything. No TV. No computers. No phones. No nothing. If needed, I would shut off the power to his room. Most bedrooms are on separate circuit breakers, and I'd flip his off. He'd be grounded.
If he want's to leave, he can. No 'allowance'. No nothing. No rides to sports. He wants to go to football practice, he can walk his butt there. Or arrange his own ride. I would do nothing for him. Nothing.
When he finds out how hard life is, when he doesn't get any free help from me... he'll either repent, and all will be forgiven... or if he's old enough to demand his own way, he's old enough to GET his own way. And go his own way, and it will be really sad, but I'll let him go.