XCOM is one of the King Companies, but they don't have the Massive Power they had in their reality. Now they have to compete with Wayne Ent. , Lex Corp, DexLabs and other powerhouses. Nit to mention Literal Empires appearing and destroying anything foreign to them.
To be honest, I have no idea how much power they actually had in their home verse, because unlike most big fictional companies, they, really didn't just expand every choice they got. And well, by apocolypse, much of the niche they themselves filled outside earth was taken over by Marsec, which formed as part of XCOM pulling back from their extraplanetary holdings due to fears of overstretching their resources. Since it's founding, Marsec became basically the central provider of high-tech military equipment, even providing XCOM gear for the various wars XCOM finds themselves fighting to fulfil their mandate.
XCOM and Marsec is connected in some form, though it isn't clear how exactly, or how deep said connections are, considering in the Apocolypse game, it IS POSSIBLE to tick off Marsec, which considering thy are the only provider of vehicles, leads usually to game over unless you have the ability to make your own, and Marsec starts off only neutral to XCOM, unlike the GOV or the local police megacorp.
though as far as King companies, they probably have their one undisputable niche being as mercenaries and security. Though I could see them getting somewhat a reputation as reverse engineering wizards, considering Nu!XCOM research group is just insane at their ability to reverse engineer tech, combined with every variant having cut their teeth at reverse engineering unknown alien technology, and doing so quite well.
