Have I Been Pwned
What is the problem you are facing?
Have 6/8 users that have been pwned when I checked them on https://haveibeenpwned.com.
And I thought it could be interesting to have an API call on https://haveibeenpwned.com/API/v2 to check if their account have been compromised and then just show them how to secure it.
Maybe with the future 2AF option :)