Open Finder
Go to Applications
Delete the old installer or app shortcut
Check the Dock and remove any shortcut there
Open Launchpad and remove the app if it appears
Open the Desktop and Trash any leftover shortcut files
Empty the Trash
Check the Downloads folder for old installer files and delete them
Check the Documents folder for any saved installer shortcuts and delete them
Open System Settings
Go to General
Open Login Items
Remove any old installer entries
Search for the app name in Finder
Delete any remaining alias or shortcut files
Restart the Mac if the shortcut still appears