If you want to delete someone’s YouTube channel, you can only do so as the owner of the account. You will need to contact YouTube and request that they remove the account.
While it is possible to have a YouTube channel deleted, the only way for this to happen is if the account was terminated due to violating YouTube’s Terms of Service.
You cannot delete a YouTube channel without an account.
You can remove a channel name from a video by going to the video’s “Details” tab and clicking “Edit.” From there, you can enter the URL of the video without the channel name.
YouTube channels can be removed if the channel violates YouTube’s Terms of Service. It’s not clear from the question how many flags it takes to remove a Youtube channel, but it is likely that it would take a lot of flags to do so.