With the latest version of Firebase Auth (0.5.2), it is impossible to delete a user.

Other Firebase Auth libraries (such as the one for Web) have a user.delete() instance method, which is missing from the Flutter implementation.

I would like to do a PR, although I do not have a iOS dev enviroment setup. I'll see if I can set one up shortly, but I think this could be a pretty trivial PR for anyone else to do!