Although Yahoo's most severe data breach apparently involved more accounts than Collection #1, this new major security incident involves almost 2.7 billion records, including 773 million unique email addresses alongside passwords associated with those addresses on various breached services.
https://www.notebookcheck.net/Collection-1-is-one-of-the-world-s-worst-data-breaches-so-far-with-more-than-772-million-accounts-affected.395116.0.html