My name is***** am sorry to hear that you are having this issue.
I will be glad to assist you with this.
Is this on your iPhone or computer?
You can reply to me here by typing in the box below please.
You'll need to delete them from the main iPhoto library. What's in Slideshows/Albums/Smart Albums are just links to the main library.
Click on the video to highlight it then ctrl click then choose trash.
did that work for you?