Since you did not specify which platform you are using (eBay, Amazon, Etsy, etc.), here is the most common answer based on how major e-commerce platforms handle blocked lists and reviews (specifically eBay, where this is a frequent question).
A blocked buyer list is a valuable risk management tool for online sellers, but it is not a perfect solution. It works best when combined with clear listing policies, responsive customer service, and platform-specific buyer requirements. blocked buyer list
Individuals who send harassing, threatening, or unprofessional messages. Since you did not specify which platform you
Buyers who win auctions or commit to purchase but fail to pay. responsive customer service