Which word best describes severe criticism or disapproval?

The word that best describes severe criticism or disapproval is censure. This term specifically refers to the expression of formal disapproval or condemnation of someone's actions or behavior. In contexts such as governmental or organizational settings, censure can be an official reprimand that highlights the severity of the disapproval.

The other options do not convey criticism or disapproval. Advocacy refers to the act of supporting or arguing for a cause, while endorsement means to support or approve of something, often publicly. Affirmation represents the confirmation or validation of something, which is a positive rather than critical stance. Thus, censure is the term that aligns closely with the idea of expressing severe criticism or disapproval.