Which word means to criticize someone harshly?

The word "vituperate" is the most accurate choice for meaning to criticize someone harshly. It derives from Latin roots that convey strong condemnation and harsh verbal abuse. This term is often used in contexts where the criticism is not only severe but also quite expressive or forceful, implying a high degree of animosity or disdain in the criticism.

The other words, while related to criticism, do not capture the same intensity. "Commend" means to praise or express approval, which is the opposite of criticism. "Denounce" typically refers to publicly declaring something as wrong or evil, which can imply criticism but lacks the personal attack aspect found in "vituperate." "Reprimand" involves a formal expression of disapproval and can be severe, yet it does not necessarily convey the same level of vitriol or aggressive language that "vituperate" evokes. Thus, "vituperate" is the choice that denotes the harshness of criticism most effectively.