So sorry you are in this situation. I can definitely relate.

I learned some techniques for dealing with people like this. Some are more effective than others. I will share them with you in the hopes that others here have more practical and effective techniques than mine.

One is called the WHAT response. It is a technique of verbal judo. When someone says something unwelcome, one responds with the word WHAT? If they repeat the unwelcome remark one says WHAT? again.

If they rephrase the unwelcome remark one says WHAT? again. If they say something like... "are you deaf" or "are you crazy" one just says WHAT? again. Respond to everything with WHAT? until they run out of steam.

The word "what" is a question. People don't expect it. They expect you to respond with a statement or hurt feelings. A statement gives them the opportunity to provoke you again. They can take any statement you make as provocative.

But "what" is a question.

It is called verbal judo because it uses the other person's strength against themselves. One yields so they fall from their own attack so to speak.

Another technique is to simply walk away for the person when they make an unwelcome remark. Leave the room. Leave the house. Go for a walk. Go for a drive.

Most people do not expect this.

In both techniques one is secretly empowering oneself by a kind of unexpected resistance. When one says WHAT? it throws the other person off balance a bit. It gives them time to reconsider their next move and possibly de-escalate the situation.

Leaving the person making the unwelcome comments is a form of distancing and secret boundary setting.

These are techniques for dealing with the other person.

There are also techniques for minimizing the pain to oneself caused by the other person.

For instance, whatever the other person has said or done, there are always worse things they could have said or done. Always.

One can attempt to convert attitude into gratitude: "Thank goodness this person didn't say something worse. Thank goodness this person isn't worse. There are worse things a person can be."

"This person could be Hitler or Stalin and cause the destruction of tens of millions of people, but they are not, thank goodness."

In the grand scheme of things this toxicity of their is pretty minor.

This is a technique for damage control when confronted with toxic behavior.

Another technique is called "Role Playing."

If one is sort of stuck living with a person who is troublesome, one can imagine that one is a doctor in one of those 19th century insane asylums and that this person is a patient.

One doesn't take seriously the outbursts and musings of the insane. Pretend the person is insane and you are doctor observing them.

This is an approach that sort of uses a sense of humor to defuse things. It is a secret joke you have with yourself.

I once worked in a very toxic workplace.

A psychiatrist suggested I see myself as a doctor in one of those 19th century insane asylums. I saw my noxious co-workers and other staff as people afflicted with insanity.

It kind of made my life fun in that situation and took a lot of pressure and misery off my shoulders.

Hopefully other members here will have "way better" ideas for you. So sorry again you are in that situation with your relative. My heart goes out to you!