(TO NOTE, MAKE BACKUPS BEFORE ATTEMPTING)
Your server should be shutdown before doing this.
1. Navigate to your control panel and open your file manager
2. Under storage {yourip/storage} download the Game.eco file
3. Using either 7-zip, WinRar or your preferred archive management software to open the file (do not unzip the file, only open, or it may not function)
4. Within the archive, you will find a "Users" folder. Within the folder are the steamID's of players on the server, delete the steamID of your choice to remove a player
5. Close the archive and reupload to your server