Delete Bank Key

1. You can use FI06 to set the deletion flag for the bank key that you want to delete.

2. You can also use Tcode OBR4 to delete all the Bank keys available in a Bank country ( This is not your requirement as i understand from your mail)

3. Setting the deletion flag should be enough, if you dont want to use the bank key that you have created. Create a new bank key in FI01 and replace the old Bank key with the new one. Transaction code OBR4 will anyway not allow you to delete, if the status of your company code is productive.

4. You can also use SE16N "& SAP_EDIT" to delete it from transparent table but of course it is not recommended.

5. You may also check FM "BANK_MARK_FOR_DELETION".

But I guess in FI06 you can set for deletion and that should be enough for you.