The President of the United States has sole nuclear launch authority. To stop him would either take the cabinet and VP invoking the 25th amendment and removing him from office, or a military officer to disobey direct orders.
Even the president needs someone else to push a button (and in those rooms there's also more than one person). There's literally no human that can do it alone without convincing at least 1 or 2 other people, depending on who it is.