Which term means "extreme excess"?

The term that means "extreme excess" is "plethora." This word is often used to describe a situation where there is an overabundance or an excessive quantity of something. For example, one might say there is a plethora of choices available, indicating that there are so many options that it may be overwhelming.

In contrast, the other terms represent concepts that do not align with "extreme excess." "Deficit" refers to a shortfall or lack of something. "Scarcity" indicates a shortage or limited availability of resources. "Moderation" signifies a balanced or measured approach, without extremes in either direction. Thus, "plethora" is the only term that accurately reflects the idea of an overabundance or extreme excess.