Monopolist

A monopolist is an individual, group, or company that controls all of the markets for a particular good or service. A monopolist probably also believes in policies that favor monopolies since it gives them greater power. A monopolist has little incentive to improve their product because customers have no alternatives. Instead, their motivation is focused on protecting the monopoly. A monopolist controls a market and is the supplier that provides a good or service to many consumers [Investopedia].
A monopolist can raise a product's price without worrying about competitors' actions. In a perfectly competitive market, if a firm raises the price of its products, it will usually lose market share as buyers move to other sellers. Key to understanding the concept of monopoly is understanding this simple statement: The monopolist is the market maker and controls the amount of a product available in the market [CFI].

Sources:

Monopolist. Investopedia. Retrieved from: https://www.investopedia.com/terms/m/monopolist.asp

Monopoly. CFI. Retrieved from: https://corporatefinanceinstitute.com/resources/economics/monopoly/