Zaibatsu is a mega corporation that owned, among other things, the White Knights and either owns or manipulates a number of media outlets such as The Augmented Eye. For all intents and purposes they run Glitch City.
Many demonize Zaibatsu as the source of everything that's wrong and corrupt in Glitch City, although Zaibatsu has also done beneficial work as well. For example they started the AI Integration Program, which has lead to countries around the world seeing the benefits of recognizing AI as citizens.
The medical branch of Zaibatsu has also made incredible advancements, with more and more diseases that were previously thought of as being incurable being treated every year. However this medical technology is often only accessible to people who can afford it and many lower to middle class citizens are left without treatment.
On the flip side, Zaibatsu's oversight of the White Knights has been negligent and they often turned a blind eye the the corp's illegal and corrupt going ons. On top of that, Zaibatsu's methods in forming the White Knights was done in such a way that they effectively existed outside of any jurisdiction and could be borderline illegal.