What to do with 2 cats in the same house that want to be the ONLY cat?
Let them settle the problem in a deathmatch. Whoever wins gets to keep the house.
A) A fight to the death, or B) get rid of one.
You need to provide more territory, and you can do that with TWO cat trees, ideally located in front of windows in two different rooms. That will give each cat a top shelf to claim, and the top shelf is prime territory. You also need at least two litter boxes. And if both are not spayed/neutered then that needs to be done. Have you tried Feliway diffusers, or the pheromone calming collars? Those can help as well. Feed them separately also - you need to provide separate things for each cat so they don't compete for the top cat spot. If after trying these, it still isn't working out, you may need to find a home for one of them as the only, and understand that the one you keep has to be the only, also. But provide the trees, the boxes, the Feliway - and it may settle down.
nnaybe you can give away one of thenn to a friend that dont have a cat and then they'll both be the only cat
kil other kity in nic gentl way. theorteckl kill not real, if no therohictcle and physcdial it pretty mean but theortecle to other cat so he tink ded but isnt