Note that you don't need to send a new event for each user you unfollow.
If you are using a Twitter clone (the main, most common and most obvious application, but not the only one), then yes, at each click a new list should be generated.
But if a tool is designed specifically to mass unfollow users, it may and should have a button to upload the list at the end of the selection, so only one new updated list has to be sent.