Cats bullying another cat will guard food, fight, stand up their back hair, and growl lowly. After the owner finds out, it is best to keep the two cats separately to avoid injuries and wait for the adaptation period. Later, let the two cats out so that they can get along well with each other.
Tips:
Generally, two male cats are more likely to fight when they meet, and the weaker one will be bullied, so try to choose two male cats. Raise cats of the opposite sex together.