We can call it "abuse of market position" then. The United States' Federal Trade Commission[^1] sued Amazon in 2023 with this pretext.

In Germany, the Federal Cartel Office fined Amazon[^2] 59 million euro (68.7 millions US dollars) because of "abuse of market power" with anti-competitive practices.

The European Commission[^3] also opened an investigation regarding Amazon's practices regarding Prime and the "Buy Box" (I had to look this up, apparently it means being picked as the default seller for a product where multiple sellers are offering it), since you need to pay extra for FBA to have your products marked as Prime (appearing before on the search results, and being the "buy box") and Amazon itself competes with you sometimes, being both a marketplace and a seller.

[1]: https://www.ftc.gov/news-events/news/press-releases/2023/09/... [2]: https://www.politico.eu/article/german-regulator-fines-amazo... [3]: https://ec.europa.eu/commission/presscorner/detail/en/ip_20_...