Spoiled 6 year old

I have a 6 year old step son who is spoiled by both his grandma and his dad. He gets away with everything never gets disciplined when he does something bad, doesn't get nothing when he throws things or hit his dad or throw things at him and nothing when he tells me to shut up or his dad, and it's getting on my nerves that his dad is more of his friend then his dad, and I'm getting tired of it, cause I don't want the same for my daughter from him. I don't want her being a spoiled kid that never gets disciplined cause they will never learn what happens when they do bad until it's to late. He throws his tablet the tv remote and the PlayStation controller if things aren't working or stops playing a video or when he gets frustrated at it. And I've been getting in him about throwing it but take it away from him for a little bit but then he throws a bigger tantrum and starts throwing his toys Ok and his chair and his dad does nothing about it NOTHING and I'm about ready to walk out cause if I do something and he gets more mad I'm the bad guy and I get in trouble by dad or grandma so I have to say in what disapline he gets, I never hit him nor will I ever I just take whatever is making him mad away from him and that's it.