If you have the Super Admin (or User Management Admin) privileges on your G Suite Account then you can access the Admin Panel and Add, Suspend and Delete user accounts from your domain.
When an Account is deleted all of the associated data in G Suite (e.g. Email, Drive items. Calendar etc.) will be permanently destroyed.
However there is a period when the account is Restorable. This used to be upto 6 days but was recently (October 2017) raised to 20 days.
In the Admin Panel