After analysis. The problem he encountered was entirely caused by his personal fault. The seller did nothing wrong.
In the process of communication between the seller and him, he refused to communicate and bear his own fault. The seller has been communicating with him in good faith, giving him a better solution as far as possible and making concessions all the time.

However, he is like a lunatic, ignoring the seller's proposal at all. Every reply he gives to the seller indicates that he will make a bad comment. Just like a robot, repeating the same words. In the end, the seller took the loss themselves and didn't want to waste any more time on him, so directly gave him a full refund.

But this problem was discovered by our team and we chose to expose this person. This is a coward. When he made a mistake, he did not want to admit it, but asked the seller to meet his rude request. He does not communicate and will only constantly threaten the seller. Until the seller can't stand it, and directly give him a full refund.

His target is some goods with moderate price and not very expensive, because in this case, the seller is more likely to give up arguing with him and eat the loss（Because accepting the return will also cause the seller's cost loss. Many sellers will be more likely to give up their products if the price is not too high.）. Therefore, he can successfully get free products. In order not to let him succeed, it is suggested that all sellers put him on the blacklist in advance.