How to Delete FTP Account in DirectAdmin and cPanel
If you are using server with DirectAdmin, in server control panel select FTP Management. To delete an account, place a checkbox next to the account you wish to delete and then click the Delete Selected button.
In cPanel server go to cPanel -> FTP Accounts, find FTP Account you want to delete and press Delete button. If you want to delete only FTP Account but keep uploaded files, press Delete Account, but if you want to delete account and files uploaded choose Delete Account and Files option.