ThutoCo is the largest company in the western world. As the source of most of the planet’s food and energy, more people rely on ThutoCo than any other corporate entity. Since the world outside the city walls is deadly, employees farm remotely by controlling robot drudges. These employees live and work in corporate provided houses and never have to leave or visit the outside world.
The Carcer Corporation was founded in Pre-Civil War America and grew into the largest private military the world had ever seen. The company is employed by many local governments as a police force. Citizens who can afford it place bounties on others and Carcer ensures their arrest, sending them to prison cities. Wardens serve as their most feared operatives, prowling the cities for the highest bounties.
At the forefront of electronic weapons, Kingfisher is the largest munitions company in the world. Providing pistols, rifles and machine guns both on earth and off-world, the company employs more people in South American factories than any other. Rather than allowing others to cannibalize their sales with knock-offs, they also produce less expensive (and less efficient) models of their products by a subsidiary company.