How do I show deactivation date? There are only a certain number of fields one can check/uncheck to show in User list page.

Is there such a field call deactivation date?  Is this a custom attribute field?  There is role expiration date when assigning user to roles but never heard of deactivation date.

There are limit number of fields that you can set visible/invisible on the User Account page.  Login as Admin and go to Admin >> User Accounts then click on User Settings link.  On th User Settings page, check the fields to display in the User Accounts Setting section.