If you have a non-guardian account, you can delete it using the Manage Your Account link on the Battleon home page.

Since AdventureQuest does not have a monthly fee, there is usually no need to cancel or delete a Guardian account. If a Guardian account is deleted, is is gone forever.  This means we will not recover the account for you if you ask us to delete it. If you create a new account later on, and wish to make it a Guardian, you will need to pay the upgrade fee again.

If you no longer wish to play your account, you can simply stop playing. There is no monthly subscription to cancel.