How do I stop repeated McAfee alerts on my MacBook Pro?

Apparently you didn't get all of the components of McAfee uninstalled. Did you run their uninstaller, or did you just drag the app to the Trash? If the latter, run the uninstaller if it's still present. If not, you can try going to terminal and using the following command:

For McAfee v. 4.8: 
sudo /Library/McAfee/cma/uninstall.sh

For McAfee v. 5.x: 
sudo /Library/McAfee/cma/scripts/uninstall.sh

to get rid of it all, but there's no guarantee that will work with some components manually removed, and those commands may not be current (they're the most recent I could find). If that still doesn't work, you may need to contact McAfee support for further assistance, though one last thing to try would be to see if you can get to your hard drive's Library/Startup Items folder and if so delete anything related to McAfee you find there.

Hope this helps. Regards.

Post the free EtreCheck report using the Additional Text option when posting. The report contains no personal information and will show the location of any files you may have missed.

How to use the Add Text Feature When Post… - Apple Community

Did you use the official uninstaller?

if no resolve

for your third party app— if in doubt search the developers website or contact their: Support/Help/FAQ/Known issues/compatibility/updates…

Contact a third-party vendor - Apple Support

Contact a third-party vendor - Apple Support

McAfee Customer Service – Official Site

McAfee/Customer service

1 (866) 622-3911

https://www.mcafee.com/en-us/consumer-support/help/common-faq.html

Third party AntiVirus is not recommended— it typically does nothing but add issues to the macOS and competes directly with Apple’s own built in security:

macOS - Security - Apple macOS - Security - Apple

Apple Platform Security - Apple Apple Platform Security - Apple Support