Sounds like the kid needs to be assessed by a pediatrician, as it sounds like he has some sort of disorder going on...

As soon as you arrive, thrash the little brat and tell him, "You're mine, bitch." Once you establish yourself as the top dog, things will go fine. I'll bet the kid will love you and request you for future babysitting.

Violence begets violence. It does sound like this kid seriously needs some testing to find out why he's violent. Chances are, it was a taught thing. If not, then he has a very serious medical condition that needs to b e addressed.

At least the parents do support you and give you the right information instead of pretending his spawn is the most perfect little angel ever born. That looks almost relaxing.

I’m so sorry you have to deal with this. I’d talk to your agency and see if you can work with other clients, or if that’s not a possibility, talk with the parents and see what can be done. I’ve been there to a lesser degree, and another thing that helps is trying a variety of bonding mechanisms so that the kid might calm down enough to actually do fun things with you, like playing games. If you can handle it long enough to figure out the children’s interests, you have a way in. Good luck

The agency needs to drop this client if the kid is so bad the parents have to pay extra fees. And the parents need to get their kid some help.

Call CPS. It's obvious the parent is neglecting the child's mental health needs.

Clearly the dad doesn't know how to parent. And if the kid is old enough to be up and damaging things, he's old enough to be disciplined. It may already be too late at this point. People like that make me so mad...