Straight: Trope Co.. manufactures everything from aircraft to zippers, tends to buy up it's competitors or drive them out of business as soon as they appear, and lobbies the government into giving it more and more power.
Subverted: Trope Co, which hyped around the galaxy as a Mega Corp. is a big pile of Overadvertised, and Overpriced stock whose main use is as a tax write off. It is incompetently administrated and dripping in debt and it's very existence is a giant Pet the Dog on the part of all the Merchant Princes around who don't deign to buy it out.
Double Subverted: That's because it is a front for Trope LIC which uses it as a place to put their useless personal, to dump all the pollution their secret factories create, and to divert attention from their own evil plans.
Parodied: The boardroom meeting of Trope Co. executives is shown - and as soon as one of them mentions a market they haven't cornered, everyone is thrown into blind panic untill the CEO screams at them to get a hold of themselves and explains how they're going to take over that market too.
Zig Zagged: The influence of Trope Co. waxes and wanes as the plot demands.
Averted: Trope Co. is a big corporation, but like in real life, it can't measure up to The Government.
Enforced: The work in which Trope Co. appears is a study of monopolies, making it neccesary to have a monopoly as an example.
Lampshaded: "Is there anything that Trope Co. doesn't sell?" "Nope."
Invoked: The country of Troperia deregulates it's economy, hoping that Mega Corps show up and bring in some tasty, tasty tax money.
Exploited: The Conqueror claims the intent to liberate people from the grip of Trope Co
Defied: The Troperian regulators have outlawed large corporations, so Mega Corps are unable to form.
As Trope Co. expands, swallowing up competitors and eventually supplanting The Government, they are forced to provide public services simply to keep their customers and employees safe, healthy, and educated enough to shop and work. Profits end up declining as more and more of the company's money is spent on maintaining and protecting the business instead of actually doing business. In the end, Trope Co. simply becomes the new government and ceases to be a true corporation. Keeping society afloat is now a higher priority than making money, defeating the entire purpose of the company in the first place.
If Trope Co. becomes a monopoly, it basically defeats the innovative purpose of laissez-faire competition, resulting in said monopoly suffering and decaying from stagnation and increasing incompetence. Eventually, the economy will collapse due to a capitalistic society's inability to function without capitalism.
Reconstructed: While Trope Co. effectively becomes the new government, it is a borderline feudal government that provides no public services to its subjects while controlling every aspect of their lives to prevent revolution. It doesn't even matter if their profits are down, since they control the value and distribution of all money and goods. The heads of the company never cared about money, just power; Trope Co. was simply a means to achieve that end.