What term describes the strongest variation of a particular beer style?

The term that describes the strongest variation of a particular beer style is "Imperial." This term is often used to indicate a version of a beer that has higher alcohol content and more intense flavors compared to its standard counterparts. For example, an Imperial Stout would typically have a richer, more robust flavor profile and a higher ABV than a regular Stout. The term originated from the 18th century when certain styles were brewed especially for export to the Russian Imperial Court, necessitating higher alcohol content for preservation and flavor.

In contrast, terms like "Full-bodied" describe mouthfeel and richness, while "Session" refers to beers that are lower in alcohol, intended for prolonged drinking sessions without overwhelming the drinker. "Classic" denotes a style that adheres closely to traditional brewing methods and characteristics, but it does not imply strength or high alcohol content. Therefore, "Imperial" clearly denotes the strongest variation in a style, making it the correct choice.