From the Mastodon Docs:
A Mastodon suspension (that is the type of ban seen in the screenshot) means the account is effectively deleted. The account no longer appears in search, the profile page is gone, and all of the posts, uploads, followers, and all other data are removed publicly. However, all the data is available in the admin back-end for a period of 30 days from suspension. This is to give the user an opportunity to work with instance admins to resolve any potential issues and have the account re-instated.
it doesn't get more permanently banned than "deletion of user profile, posts, followers and uploads"