If you are a Roblox game developer, you can only see banned users data if you have implemented a custom ban system in your game (such as saving banned logs to the DataStore). Roblox by default does not show you banned users of other games. But if you have made your own game, you can create a script in the studio or admin panel from where you can check the list — such as showing the ban list in the GUI or printing it in the console log. This data is not visible to public players.