There is a vast number of corporations and companies, who, following WWIII and the destruction of many others, managed to rebuild, incorporate or cannibalize others to relevance. These Gigacorporations are either enormous conglomerates of smaller corps, or singular, nation-defying powers with trillions of credits to their name.
Born from the union of the tech companies Toshiba, Vobis and Olivetti, TriStar Systems found its call in the invention of the first true AIs and the mass production of several robot lines. TriStar's multinational nature has allowed it to surpass most disagreements and conflict and prosper even following WWIII. The CEO is Johan Wenz, an unshakably serious Lunar-born who has, in the past, fiercely rejected new ideas and has instead kept TriStar as a purely tech, robotics and electronics company. TriStar operates a wide automated fleet which mostly focuses on passenger transport and delivery. It operates an affordable on-call robotics repair service managed by the TriStar Bulk Carrier Ryujo, known for making the rounds in Sol every week.
Whereas TriStar is often considered as a company employed in the production of fine-tuned, elegant hardware, Hephaestus Industries is the opposite. The company, a large conglomerate of several industrial corporations including Volkswagen, Chevron and Saudi Aramco, is mostly in the field of large heavy-duty engineering projects, such as starship construction, colony installation and similar. The CEO, William Steele, is a fitness guru who embodies the company's fervent drive to produce in unthinkable quantities. Calling himself "God of the Forge," Steele frequently holds speeches and has personally worked on several projects. The Hephaestus Superstation Olympus, orbiting the Sun, is the main office of the company and the largest starship repair facility in the galaxy. Hephaestus has its own line of robots, mostly engineering and combat-focused, and some military subsidiaries:
Norinco-Sukhoi and SAAB, two fighter and assault drone producers,
Rheinmetall, a large-caliber weapon manufacturer,
Dassault Naval and Mitsubishi Heavy Industries, military shipbuilding agencies.
Jincan is a gigacorp originating from China, with ties to an underground cartel that smuggled medicine during WWIII in and out of the country. It technically is not a single corporation, but a large number of small, specialized companies that report to Jincan as a whole, in what is best described a near-pyramid scheme. Their CEO, Xihua Hsiao-Li, has apparently spoken a total of four words since taking power, and exerts a ruthlessly efficient power over the company via her subordinates, who, rumors claim, are psionically controlled. Jincan's main constituents are Renshi Biotech, which focuses on organic and robotic augmentation and prostheses, and Gongjun Genetics Innovation and Research, which focuses on cutting-edge genetics research and modification. Of note is also the Jincan Medical Response Service, a costly insurance service that responds to calls for medical assistance. Jincan's main base of operations is a Lunar colony named Lianmin-1.
Founded by William Idris, an African lawyer, after the onset of WWIII, BFM promised what Switzerland previously did, before being destroyed. It was the idea of a semi-legal asset retention company and private bank that attracted an infinite number of radiation-afflicted millionaires and desperate influencers who poured their money into it to keep it safe. Using a clause in the contract, once the WWIII survivors died of their injuries or overzealousness, the money went directly to the company. Still a rather patriotic man, Idris routed some of the profits of dead Westerners to the newly founded South Hemisphere Coalition, and helped fund the construction of Korosude, the capital. Nowadays, the company thrives off of the dizzying amount of money it still has from the war, effectively operating at a loss for almost 30 straight years. It is known for approving risky loans and financing auspicious projects "out of curiosity" as expressly stated by William Idris.
While BFM officially states for Banking Fund of Maiduguri, William's home town in Nigeria, it is also quite commonly assumed that it actually stands for "Bebe Farin Mutum," which in Hausa, Nigeria's official language, meant "dumb white man."
GSS, much like Jincan, is a conglomerate of a number of companies grouped into a large corporation. Founded by Lyudmila Korzakov, a Russian PMC owner and rumored Russian intelligence agent, her rise to power and the foundation of GSS took the form of a crusade against other PMCs. Employed by the Russian Federation originally, her PMC operated in Africa but pivoted to Asia, incorporating or destroying rival companies until Russia's revolution, when she was officially banned and labeled an enemy of the state. She has expanded GSS's reach to the stars, even being contracted by some Kosidian nationals. GSS encompasses a number of companies:
Uralkumar Arms, a small arms manufacturing company,
Sekhmet Intelligence, a cybersecurity agency,
Ringspire, a de facto army with a small space navy,
Nexus Security, focused around VIP escort and similar,
Sicario Squadron, a company made up of privately owned fighter aircraft.
It's still there.