HOW TO STOP MY CAT FROM BULLYING MY OTHER CAT
Cats might pick fights if they are intimidated or if they see the other cat as prey. One of your goals should be to help both of your cats feel more confident.
Set up lots of cat trees, condos, and window perches around the house. You want your cats to have the option to escape to higher ground, so they're not always forced to walk directly past each other. Look for places where one cat typically corners the other and try to put a cat tree there. This can also give your cats more space to call their own.
Consider getting more litter boxes since cats can be pretty territorial about where they pee. Try one litter box per cat, plus an extra box.3 You might also want to use litter boxes without tops so one cat can't get cornered by the other.
Separate their food and water bowls too. Cats have an instinctual need to protect their food, so forcing them to eat out of the same bowl may create unnecessary tension.
Re-Introduce Your Cats
If things have become really tense between your two cats, you may have to introduce them all over again.4 This process might take a few weeks, but it will be worthwhile in the long run. Start by keeping them in separate rooms and swap blankets so they get used to the other's scent in a non-threatening environment. Feed them on opposite sides of a closed door. When they can eat calmly, try feeding them on opposite sides of a gate or screen door.
Once they've graduated to being calm in this situation, you can supervise visits in the same room. Give them their favorite treats and see if you can use toys to distract them from each other. The goal is to teach both cats to associate the other with positive experiences, eventually learning that they aren't threats.
Just like people can get into fights, cats can too. A wrong meow or a shared litter box can be enough to cause tension and bullying. And just like people may need a little intervention to get along again, your cats might need a little help as well. With patience and time, your fighting cats will make "pawsitive" changes and become friends again.