How do I delete a reference file?
To delete a video using SFTP, you can submit an XML content feed that identifies the video that you want to delete. In the feed, the value of the <yt:keep_fingerprint> tag indicates whether YouTube will continue to compare user-uploaded videos to the fingerprint for the deleted video to generate claims for your account.
YouTube's default process when you delete a video is to convert the corresponding reference file's status to inactive, meaning that YouTube will no longer claim for your account new user-uploaded videos that match the deleted video.
If you do not have access to SFTP Dropbox, you can deleted a video through the steps outlined here