Which word means to kill or destroy a large portion of something?

The word that means to kill or destroy a large portion of something is "decimate." This term originates from the Roman army's practice of killing one in every ten soldiers as a form of punishment or to reduce the numbers in a unit. In contemporary usage, "decimate" has broadened to refer to the act of significantly reducing or destroying a substantial part of a group or population, whether that be in terms of resources, wildlife, or other entities.

The other terms do not convey the same meaning. For example, "deride" refers to mocking or ridiculing someone or something, which is unrelated to the idea of destruction. "Deluge" typically describes a flood or an overwhelming amount, focusing on the context of flooding rather than destruction. "Deplete" means to use up resources or reduce the quantity of something, but it does not necessarily imply destruction on a large scale. Thus, "decimate" is the only word in this context that accurately aligns with the notion of widespread destruction or reduction.