We had a neuropsych eval and they recommended reading the book "Your Defiant Child" https://www.amazon.com/Your-Defiant-Child-Second-Behavior/dp...

It's been helpful and was initially counterintuitive. I think the author has one for teens as well.

This may not apply to your situation but the parents have to be on the same page as each other and have a mutually respectful parenting style otherwise things will appear unstable and the kid will exploit that loophole.

Also for all behavioral problems, the only person you can change or control is yourself.

And remember that every behavior is a form of communication of some underlying need.