Delete a bank account

What you do is make the entries that match reality for activity in that account, reconcile that account to the financial institution statements, show it is at 0 if you closed it in reality. Then you Make it Inactive, and it stops showing. You cannot delete something that has been used; it isn't just the banking side of the activities. The Banking side represents the purchases, sales, etc, that also is part of each transaction. You don't delete all this activity, unless it never should have been part of the file, to start with.

Why do you need to make it go away?

I have 2 bank accounts. 1 and 2. transaction which are supposed to go to bank 2 went into bank 1, I have added all transaction to bank 2 manually and now I want to get rid of bank 1 entirely 

For this, "I have added all transaction to bank 2 manually"

You would have opened the transactions and changed the bank account they were assigned to.

Now that you have Duplicate entries, you delete the individual entries from the Wrong Location.