I wouldn't let this person adopt from me after what they did to an adoptable artist I know (they called him a Scammer for selling an adopt before they could ask to buy it). Suggested action, block and move on, don't do business with this person.
Meanwhile, Goldeye-and-Cory (https://www.deviantart.com/goldeye-and-cory), I'm sorry you had to deal with such a terrible adopt-troll.
Their journal: they hid all their own comments on the adopt btw