In the app: Account → delete account. It asks once, then does it.
Without the app: email [email protected] from the address on your account. We will verify it is you, then delete it.
Your profile, your group memberships, your answers, your messages, and your device tokens. Plans you proposed are deleted, along with the answers other people gave them.
Groups you created are not deleted — they pass to whoever has been in the group longest and carry on without you. If you were the only member left, the group goes too.
Deletion cannot be undone. Full detail in the privacy policy.