Duplicate Cleaner is a free (with a pro paid version) app that finds and cleans up duplicate files on your computer. You have some advanced options, such as same content/ignore content, same name, similar name, same size, and different combinations. It works on your local drive and even enterprise network drives.
I have tons of duplicate files because of changing accounts, backups, etc. that this helped me clean up.
I also have duplicate files in my Google Drive account for the same reason (uploading from different sources). Since I sync Google Drive to my laptop, I ran Duplicate Cleaner there and cleaned up the duplicate files.
There are some nice tutorials and a manual to help you out.