Will child support garnish the whole tax return?

Yes, it will be so confiscated if the state court has filed the appropriate paperwokr with the IRS.

For sure, the STATE tax refund will be confiscated.

ALL of it!!

It is all of it, but if there is another individual on the tax return, they can file to papers to get their part back. I am sure that it will take awhile for the papers to be sent, filed and money to be sent back.