Try the following:
1 - download Find Any File.
2 - boot into Safe Mode (How to use safe mode on your Mac - Apple Support) by booting with the Shift key held down.
NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing.
The reason for booting into Safe Mode is that it blocks all 3rd party software from running, thus allowing it to be safely deleted
3 - launch Find Any File and search for any files with the application's name and the developer's name in the file name. For example for CleanMyMac software you'd do the following searches:
1 - Name contains cleanmymac
2 - Name contains macpaw
Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.
FAF can search areas that Spotlight can't like invisible folders, system folders and packages.
There is no reason to ever run any "cleaning", "optimizing", "speed-up" or anti-virus apps on your Mac. This user tip describes what you need to know and do to protect your Mac: Effective defenses against malware and other threats - Apple Community