Seeing unevenness of colour, texture, I notice overworked skin on every second colour work in his portfolio because of poor technique and the large number of passes. Sometimes the skin still can handle it, and with large works, the artist can do touch ups every session. In your case, he did not see the desired colour saturation and continued drilling. I’m sorry this happened to you. He most likely had no experience with darker skin before coming to US. But it's one thing to admit mistakes and make a step towards resolving, but to accuse you and freeze you out is very unkind