How to End-Date/Delete an Applications User ???

Applications users cannot be deleted since records belonging to users are kept for security and monitoring purposes. In addition, the user is recorded in Who columns, so deleting would cause foreign table data integrity problems. Instead, set "End Date" for that user.

Also same for the responsibility. We cannot delete a responsibility. We can only end-date a responsibility.

So Users and responsibilities cannot be deleted, instead you should end-date it.
For menus, functions, custom applications, it is to delete them -- Navigate to the form, query the record, and click on the delete button (or Edit > Delete).

There is no API or scripts to delete user accounts in FND_USER. Deletion of an an e-business suite user account is not possible and not supported. The supported methods to disable an Applications User are:
1. To end-date the user account from the Define Users forms or using the following API :

• FND_USER_PKG.UPDATEUSER you may pass an end date to the parameter X_END_DATE of the procedure FND_USER_PKG.UPDATEUSER.
  This will disable the user account.

The example below shows how to end-date custom user PIERRE:

fnd_user_pkg.updateuser(x_user_name=>'PIERRE',x_owner=>'CUST',x_end_date=>SYSDATE);

x_owner can be either SEED or CUST:

• To end date seeded users (i.e. sysadmin) x_owner= SEED
• To end date custom users x_owner = CUST

2. To use FND_USER_PKG.DISABLEUSER API:

• Pass the username as parameter. This will disable the user.
  

Note : After disabling a user, you can enable it by using the package FND_USER_PKG.ENABLEUSER