all you want = as much as you want; without limit Deny it all you want = You can deny this as much as you want (without limit), but it remains the truth.

"all you want" is an emphasis on the verb/action so, when we say "ok deny it all you want!" the meaning is just, deny it as much as you can, but I will STILL buy the finger print kit here is another example: Child: Mom, I promise I will do my homework later, let me go out with friends Mom: Promise all you want, you are going to finish your homework first! So, the "all you want" is emphasizing the "promise"... that no matter how much the child promises to do homework first, the mom will not allow him to go out Lastly, we also can say this for "eat all you want" "drink all you want" basically meaning eat until you are full or drink anything you wish to drink

It means that you can keep denying it but I don't believe you. I believe that you did it.

I agree with Kevin