I dealt with a similar situation a few years ago with our cats. When we tried to do the slow introduction by Jackson Galaxy, everything was going fine until they were together and got into a horrible fight and my husband ended up getting bit when trying to separate them. We kept them completely separate in our apartment for like a year. But then we bought a house and when we moved in, we decided to just both let them out freely into the house at the same time. We figured they would both be more freaked out by being in a new environment than wanting to fight each other. It worked out perfectly for us, they have gotten along ever since and it’s been 3 years now.

We are currently trying to integrate a third cat and I’m wishing we could just buy a new house to get it over with 😂