If you wish to completely delete your account information on your iOS device, please go to Avatar - Settings - Delete Account.
The Account Deletion process might take up to 1 month (typically within 24 hours).
Please read all terms listed on the Account Deletion screen before proceeding, and the request can not be undone as per Apple's policy.
Your account/game will freeze during the process, and you can create a new account on the same device afterward.