Oligopolist

But through the oligopoly, charcoal fuel proliferated throughout London's trades and industries. By the 1200s, brewers and bakers, tilemakers, glassblowers, pottery producers, and a range of other craftsmen all became hour-to-hour consumers of charcoal. This only magnified the indispensable nature of the oligopolists.

Source: wiktionary

“As a classic oligopolist, Moody’s earns exceedingly high margins while paying only the needed lip service to product quality.”

Source: wiktionary