If I understand you well, you want to create registered accounts as an admin via the back-end, have these accounts active until the related users log in for the first time, then you want to have the related account(s) completely removed, i.e. not just disabled, upon first log-in of the user(s).
This functionality does not exist at present.
A functionality that does exist at present: if you let a user register himself (via the front-end 'create an account' option) and have this user disabled or removed upon activation of the account and upon first log-in (provided the first log-in is more than 1 hour after registration). But I understand that you are the one who creates the account (as an admin), so this would not help.
The desired functionality could be included by some additional coding. Before I do this, I would like to learn more about why you would want such behaviour. Please send me an email to This email address is being protected from spambots. You need JavaScript enabled to view it. if you want to discuss this.