Downgrade nVidia Shield to Android 4.4 KitKat I mistakenly installed 5.0 Lollipop on my nVidia Shield tablet, and I regret it. Is there a way to revert back to KitKat? I've tried finding a way, but no luck so far.
One way would be to flash a factory image to your tablet, which would restore it to the state it was when you first bought it. 

Depending on your model (wifi, or wifi + lte), you can find official factory images to for the SHIELD tablet on this nvidia website:

https://developer.nvidia.com/develop4shield

Following the relevant links, you will get to a website from where you can download the factory image. The bundle should also contain instructions. Hope this helps.