If you found your data in a list like this, you should immediately:
It looks like you are referencing a file name for a —a collection of usernames and passwords often used for unauthorized access (credential stuffing) against Riot Games accounts [1, 2].
Set up Two-Factor Authentication through your Riot Account settings. 2 Million UHQ Userpass - Riot All Targets (9).txt
Use a unique, complex password that isn't used on any other site.
Distributing or using such lists to access accounts without permission is illegal and violates terms of service [3]. If you are looking to secure your own account or create professional documentation regarding cybersecurity, here is the appropriate way to frame this topic: For a Cybersecurity Report If you found your data in a list
Verify if your email address has been part of known public data breaches.
If you are documenting a data breach or a security audit, use professional terminology: Distributing or using such lists to access accounts
Analysis of Credential Leak: 2 Million Entries (Riot Games Targets)