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These programs have a quirk in that they sometimes remove system files, resulting in a non-bootable system and a pain to figure out what's wrong.
 
As others have stated, I would avoid this for a variety of reasons
  • Not really needed
  • Can cause more harm than good
  • Other options are better/free

If you really want to use something, consider using:
  • Malwarebytes
  • OnyX
  • AppCleaner
 
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