Keyword stuffing is regarded as a good way of black hat SEO. To rank, a website up on the search engine result page (SERP) keyword stuffing is a good process. Keyword stuffing is a way of injecting more keyword in the content. Usually, upto 4% keyword in the content is natural. but if we put more in our content is would be deemed as keyword stuffing. when a crawler comes to the website it watches more keyword so it enables your site to show on high-rank position. But, you might face a penalty for keyword stuffing. So you need to do it perfectly