In order to remove/uninstall the Megascans plugin from 3ds Max, you will need to perform the following steps:
- Close both Bridge and 3ds Max.
- Goto C:\Users\<user>\AppData\Local\Autodesk\3dsMax\20XX - 64bit\ENU\scripts\startup
- Delete the Quixel.ms file.
- In Bridge, goto Bridge > Edit > Settings, and browse to the folder specified in the Library Path.
- Goto support > plugins and delete the max folder.