From the game (quickest): log in, open Options and choose Request account deletion.
If you've forgotten your password: press Forgot password? on the game's login screen to get a reset link by email, then log in and ask from Options.
If you can't log in at all: send a message asking for your account to be deleted, with your email (or username) and your hero's name. To make sure nobody deletes someone else's account, we may ask you to confirm something only the owner would know, such as your hero's combat level or what's in their bank.
Contact: use the support link on the app's App Store page.
Your account and hero are deleted within 30 days of the request, including your saved progress. Reports you made or that were made about you may be kept for moderation.