How to remove an offline emulator from avd devices?

When I am facing the same issues than doing like below:

1. Restart adb by issuing adb kill-server followed by adb start-server in a command prompt
2. Disable and re-enable USB debugging on the phone
3. Rebooting the phone if it still doesn't work.

99% of my issues have been resolved with these steps.

I have this problem on MacOS and solved it by

1. Open the Spotlight search: Press Command + Spacebar
2. Type Activity Monitor
3. Open the Activity Monitor
4. Search for qemu
5. Force quit the qemu process

Restarting adb like an answer above did not help.