How do you deal with a chronically I ll person you are helping, who is disrespectful and angry ?

Let it bounce off you and try to not be affected by it. Make sure you don't react to it at all or respond and always give them zero reaction and acknowledgement to their frustration because it encourages that behaviour

With patience, respect, acceptance, and making lots of time for yourself.

Just leave them to it.

You need some time apart. If this person is a senior with dementia, some facilities offer respite care to give the caregiver a much needed break. Or, if they have cancer, look into hospice care.