You can’t uninstall Karabiner-Elements from your Mac directly from the Applications folder. If you tried so, you will see the alert, “the operation can’t be completed because the item karabiner-element.app is locked”. The proper way to remove Karabiner-Elements from Mac is to make use of the built-in uninstaller. Here is how you can use the uninstaller to remove Karabiner-Elements from your Mac system.
Run Karabiner-Elements on your Mac, you will see its icon at the top menu bar. Click on the Karabiner-Elements icon, then choose Preferences from the drop-down menu. When the Preferences window opens, switch from the Simple modifications tab to the Misc tab. Now you can launch the uninstaller by clicking the “Uninstall Karabiner-Elements” button. A confirmation dialog pops up, “are you sure you want to remove Karabiner-Elements?” Click OK button to confirm and uninstall Karabiner-Elements from your Mac.