When the event needs payment, if a subscriptions is not completed, users still see they are registered. So if I cancel my payment (by mistake or anything else) in the middle of the processing of payment, when I get back to the website and event page, I see I'm registered.

That forces users to cancel their subscriptions and try to register again. Is there a way to avoid this happen? I want if subscription is incomplete, to be deleted automatically.

What works in my situation is adjusting the attendee module to output as a table with whether the user is paid or pending and then link the word "pending" to take them back to the payment page so they can make payment at a later date (that URL is in the database so it is pretty easy to link back to the payment page).

1	Steve	Paid
2	Joe	Pending

And you can make the table sortable by heading column using the some existing javascript packages.