Duplicate places enhanced versions of Copy and Paste into the Finder. They behave similarly to those that are already built in, with the exception that they are a lot more powerful. With this you won’t get failed copies on large folders, and you wont get any problems with permissions. It is also about 10% faster.
It will make an exact duplicate which perfectly passes the backup bouncer test, which is a test that determines whether a perfect copy of a file and all associated data is made, which many things (including the Finder’s native copy and paste) fail.
Go into System Preferences->Extensions and uncheck it there. Drag and drop the application to the trash in the Finder. It is entirely self contained and this will remove everything.