Tough question! They are all potentially severe, so it’s difficult to point to just one, but  I believe that the vulnerabilities we found on antivirus products, and the ones that we found on major brand laptops (directly from their supply chains) would have the most impact as they impact millions of users.
Most software vendors we inform about vulnerabilities are fast to mitigate and patch. Users around the world need to be faster and more diligent to install updates and patches.