Answer: Category killers
Explanation:
A specialty store as the name implies, is one that specializes in a certain category of goods. They however provide a range of products and brands within that category.
When a specialty store becomes really big and provides a very deep assortment of a particular line of goods along with very knowledgeable staff to help, they become known as Category killers because they would be providing a whole lot of brands and products under the category they operate in.
An example would be BestBuy or Home Depot.
