Which type of security control is best suited to reduce the threat of compromised credentials for Charles?

The best choice for reducing the threat of compromised credentials is multi-factor authentication. This approach enhances security by requiring users to provide two or more forms of verification before granting access to accounts or systems. By combining something the user knows (like a password) with something they have (like a mobile device) or something they are (like a fingerprint), multi-factor authentication significantly reduces the chances of unauthorized access, even if a password is compromised.

In contexts involving security measures, the other options play important roles but do not directly address the threat of compromised credentials as effectively as multi-factor authentication. Zero trust is a security model that assumes no one should be trusted by default, which is beneficial for overall security practices but does not specifically address the issue of credential compromise. Access control lists manage permissions based on user identities and resources but do not enhance the verification process during login. Encryption protects data both at rest and in transit, securing the data itself rather than the credentials used to access it. Therefore, multi-factor authentication stands out as the most effective measure to directly mitigate the risks associated with compromised credentials.