Permanently Delete This File from Trash with Terminal

1. The file could simply still be open by something. Use lsof <file> to see which process is hogging it, if any.
2. Otherwise sudo rm -rf /.Trashes/501/Users/myusername/Desktop should get rid of it
3. If that didn't work, try removing all the flags it's complaining about first: chflags nohidden,nosappdn,noarch,noschg <file>

Probably the easiest thing to do is to just boot up in Safe Mode and then empty the trash.

Boot into Safe Mode

Follow these steps to boot your Mac into Safe Mode:

1. Fully shut down your Mac
2. Restart your Mac
3. Immediately press the Shift key and keep it down
4. Let go of the Shift key when you see the login window (NOTE: If you have FileVault enabled you may need to log in twice).
5. Once you're logged in, empty the trash
6. Exit Safe Mode by restarting your Mac as normal

Next up is Apple steps to repair the disk:

• https://support.apple.com/en-us/HT201583

Basically you boot to recovery and repair the disk in question.

[EDIT]

If all the above steps fail to empty the items from Trash, then the following options are available to you:

• Reboot your Mac from another boot drive (e.g. an external USB hard drive, etc). Once logged in, your Mac will see its internal drive as just another hard drive and you will be able to empty its Trash.
• Reboot your Mac in Target Disk Mode and connect it to another Mac. The other Mac will see it as an external drive and you should be able to empty the Trash.
• Create another Admin user account for yourself and then reboot your Mac and login to your new account. Start using this account instead. It will have access to all your apps and you just need to transfer your data across. When the time comes, delete the other user account.
• If you're familiar with Terminal/Bash, and you have a full Time Machine (or other) backup of your system, you can also boot into macOS Recovery and access Terminal from the Utilities menu. Then run the necessary commands to gain read/write access to your usual boot volume, navigate to the correct user, and try deleting the Trash.