I assume you mean from your database. No, there is no way to delete all of your players at once... unless you wish to delete your entire database (meaning delete all players, leagues, and seasons). If this is what you want to do, delete the folder named "db" in the Tournament Director folder. Usually this is "C:\Program Files\The Tournament Director 2\db". You can delete it, or just rename it to be on the safe side. If you change your mind later, you can rename it back to "db".
Make sure the TD isn't running when you do this.
