This upscaler is not mine, all the credit go to: Nmkd

Official WiKi Upscaler page: Here

License of use it: Here

This upscale works better with realistic images.

For Anime style, I suggest you to use 4X Ultrasharp (you can find it in suggested tab)

HOW TO INSTALL:

Rename the file from:

4x_NMKD-Superscale-SP178000_G.pt to: 4x_NMKD-Superscale-SP178000_G.pth

Copy the file 4x-UltraSharp.pth inside the folder: "\YOURSTABLEDIFFUSION~FOLDER\models\ESRGAN")

Restart you Stable Diffusion

Now in "Extra Tab" you got the new upscaler