Final answer:
Windows 8 introduced the controversial start screen using the metro user interface.
Step-by-step explanation:
The operating system that introduced the controversial start screen using the metro user interface is Windows 8. Windows 8 was released by Microsoft in 2012 and it featured a touch-centric interface called Metro, which was later renamed as the Modern UI. The start screen in Windows 8 replaced the traditional start menu and displayed tiles of apps and shortcuts in a grid-like layout.