You might try re-introducing them. Separate them for a while, keeping them on differing sides of a door. When my cats had probs, I put up chickenwire on the kitchen door and kept one in the kitchen. That way they can see and smell each other but not get to each other. Then what you do is feed them on either side of the 'door' but together. Try giving them their fave food, or the older cat, the aggressor, its fave food, this is to associate treats with the little one. Swap smells by petting the kit then the cat, or rubbing a sleeping blanket of the older cat along the kitten, so older cat gets smell of kitten when she is all comfy and on something familiar. Feed them treats together. Do this for a fortnight or so until they seem comfortable approaching each other. I know it seems like a lot of work, but attaching chickenwire to an open door isn't hard or complicated and this important.
I haven't seen the video cos I don't like clicking on links, but if the attacks are vicious, you MUST separate them before the kitten gets hurt or killed. It does happen.
Good luck!