Long time dog owner here.
We once had a dog who was wonderful to us. But he nipped at everyone else. We brought in trainers, behavioralists, and a couple other experts.
Finally, our vet pointed out the obvious: “That dog ain’t right in the head.” We had to put him down.
Nearly 50 years of dog ownership…and this was the only one we could not control.
Sometimes they just ain’t right in the head.
I adopted a cat we named “Moe” after a co-worker’s husband found him on his UPS route; tiny, abandoned and alone. I don’t think he was fully weened yet.
FWIW “Moe” was short for Muhammar the Terrorist (my husband gave him that name) for his penchant as a kitten to lay in wait and then jump out and literally bite our ankles and I mean bite as in sometimes drawing blood. And he loved “chewing on, biting my fingers” but when he was a tiny kitten, I thought it was “cute”.
But I really started seeing even more signs of his aggressiveness and strange behaviors really coming out after he was neutered. Without provocation or warning one day he attacked our Husky with whom he had had up to then gotten along with, and he would growl and hiss at my husband who had been nothing but kind to him. Moe would also drag my sweaters and underwear out of the clothes hamper and dry hump them which I thought was very weird.
It came to the point that I was the only one who could handle him, and some people refused to come into my house unless I locked him up in another room because he would glare at them and stalk them. I was the only person who could pet and snuggle with him, but he’d purr so sweetly when I held him, I ignored the danger.
The day Moe attacked me, and I mean attacked - growling, baring his teeth, hissing, lunging at me repeatedly, gashing my leg open through my jeans, trying to climb up me to get to my throat as if he was rabid like Cujo, and I was honestly afraid he was trying to kill me. It was terrifying.
I had been petting another cat that kept coming to our door and who I put in our garage and was feeding, hoping to find her a home, shortly before coming into the house.
Moe came up to me in a friendly manner at first but then kept sniffing me and suddenly turned aggressive.
I managed to run outside the house to the porch but Moe inside at the window still growling and hissing at me, completely out of control and acting “possessed”.
After I adopted sweet pregnant cat, Zelda that I had been petting and trying to find a home for, that seemed to set Moe off (jealousy?) after my husband and a neighbor captured him and took him to animal control and we allowed them to put him down after a 24 hour hold , I talked with our new vet about Moe, and she told me that if a neutering is not done correctly and completely it can cause hormonal imbalances and some of the behaviors I described.
She also said that just like people some cats, can suffer from a sort of mental illness or brain damage and sometimes they are just “bad” and as you said, she said, paraphrasing, sometimes they “just ain’t right in the head”.
BTW, Zelda was the sweetest cat ever and she and the 3 kittens she gave birth to helped me heal from the trauma.