There are two ways from here to take back control properly from the EU on 1 January. The first is to do so by an Agreement about our future relationship. This would not only include a Free Trade Area but would also end the residual jurisdiction of the ECJ , end the payments to the EU and end any further ability of the EU to tie us to their laws.
The second is to leave without an Agreement and pass a short confirming Act of Parliament removing the remaining powers of the EU. This would build on the essential assertion of Parliamentary sovereignty in Clause 38 of the Withdrawal Agreement Act, confirming the notwithstanding clause over all residual matters.
I assume given the view of the EU it will need to be the latter. Far from undermining our standing in the world such an Act would be seen as a sign of strength by the UK, clearly setting out our independence. As the Supreme Court and the Commons has confirmed, the UK Parliament can make these laws and lead our country in the way required by the referendum decision.