I would get a large plastic or metal cage and put food and water, a bed, and of course a litter pan and litter in it. Leave a couple of cat toys in the cage too.Then cover it except for the front. The problem cat will feel more safe and secure with this setup. Whenever you go past the cage...
When this situation starts to develop, hiss at the offender and growl knock it off or something similar. Stare for a moment at the cat youre reprimanding. As soon as that cat breaks eye contact with you and moves away from the situation, praise the cat and give the cat a treat.
