MacKeeper is notoriously difficult to delete and unless carefully and thoroughly expunged is reputed to leave bits parts and pieces around that apparently sometimes recreate/redownload/reinstall MacKeeper or at the very least have a deleterious effect on system performance. The removal instructions on MacKeeper's web site are generally conceded to be incomplete at best. A Google or DuckDuskGo search on how to remove MacKeeper will return a LOT of hits from places like OS X Daily, MacWorld, iskeysoft, YouTube, WikiHow, the Official Appple Support Communities, and many more. One of those links should exorcise the demon.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein