I experience disgust and contempt towards someone in my life and I don't know how to proceed.

This person was an abuser throughout my childhood, and they still abuse my grandmother (screaming, uncontrollable emotions). My grandmother also abused them when they were a child.

They have recently (seemingly) started seeking to change because they are incapable of getting along with much of society. I do however feel contempt when I hear them talking about change, because of many failed promises throughout the years where they begged and promised that they would change from their horrifically emotionally unstable ways, but in the end only got even more increasingly unstable and even physically violent.

I think I also experience disgust because of the person's habits- they are unable to comprehend the modern paradigm of boundaries, or even why the things they do rub people the wrong way. They repeatedly refuse to respect boundaries even when told to stop, and this incites a combination of disgust, anger and panic within me- which often leads to explosive arguments.

Even though I feel mostly panic, revulsion and anger when communicating with them, I do notice that I personally have a nasty tone of contempt in my voice when talking to them. I DO NOT like this aspect of myself, regardless of what they have done

I am worried that the disgust and contempt I feel towards this person may become a poor habit and influence the ways in which I treat others.

I do not know how to approach my own contempt and tone. What are some TRP-based first steps I can take towards rebuilding my speech patterns, habits and perceptions?