This is common sense to any Apple Genius, long-time skilled Mac user, and virtually all Mac writers. But for anyone new: don't install MacKeeper. If proof is needed, start here, but any Google search will suffice.
I will expand on Darth's comment with a link to how to uninstall it. This one was updated in 2019 by Lifewire, so it's thorough. I help colleagues clean up their Macs, and as other sites have noted, there are often deep files that remain of this asshat app, so if you want to find all of them, also download the free appcleaner app from the developer: https://freemacsoft.net/appcleaner/
Handy for just such a situation.