How do I delete the avast security application from a MacBook Pro

They have uninstall instructions on their site:

https://support.avast.com/en-us/article/Uninstall-Mac-Security

Edit: Too slow! Bob was a couple of seconds faster. 😀

Use the official uninstaller.

You may have to re-install it, if you deleted it.

https://support.avast.com/en-us/article/Uninstall-Mac-Security

Using their uninstall instructions would be the best way.

: )