“Probably Susan Rice.”
As National Security Advisor, Rice would have been even more authorized to unmask, and did. She may have wanted more credited to Power, and as former UN Ambassador would have known how to work around that system using POwer’s credentials.
Another possibility would be Valerie Jarrett. Not sure if her position afforded her the same level of security clearance the others had.
I think ValJar held the highest clearance in the administration
The ‘” Do You Know Who I Am?” clearance