First, never use any kind of "anti-virus" or "anti-malware" software on a Mac. That's how you cause problems, not how you solve them.
"MacKeeper" is a scam with only one useful feature: it deletes itself.
If you have incompletely removed MacKeeper—for example, by dragging the application to the Trash and immediately emptying—then you'll have to reinstall it and start over.
Note: These instructions apply to the version of the product that I downloaded and tested in early 2012. I can't be sure that they apply to other versions.
IMPORTANT: "MacKeeper" has what the developer calls an “encryption” feature. In my tests, I didn't try to verify what this feature really does. If you used it to “encrypt” any of your files, “decrypt” them before you uninstall, or (preferably) restore the files from backups made before they were “encrypted.” As the developer is not trustworthy, you should assume that the "decrypted" files are corrupt unless proven otherwise.
Please back up all data before making any changes.
In the Finder, select
Go ▹ Applications
from the menu bar, or press the key combination shift-command-A. The "MacKeeper" application is in the folder that opens. Quit it if it's running, then drag it to the Trash. You'll be prompted for your login password. Click the Uninstall MacKeeper button in the dialog that appears. All the other functional components of the software will be deleted. Restart the computer and empty the Trash.
☞ Quit MacKeeper before dragging it to the Trash.
☞ Let MacKeeper delete its other components before you empty the Trash.
☞ Don't try to drag MacKeeper from the Dock or the Launchpad to the Trash.
☞ Don't try to remove MacKeeper while running in safe mode.
