Kalimo
Kalimo · com.sincera.kalimo
Profile → Account → Delete account
This cannot be undone and it deletes, in one go: your progress in the cloud, your study log, your leaderboard row, your account summary (your email address included), all of your learning data on the phone, and the account itself created by signing in with Google.
Write "delete my account" to ertaneker@gmail.com from the Google/Apple email address you opened the account with. The request is completed within 30 days and you are told at the same address when it is done.
Deleting the account does not cancel the subscription. Cancel it from your Google Play or App Store account settings — see the terms of use.