Providence

Providence was created after the Nanite Event, and it was the original purpose of Providence to contain and/or kill EVOs. When Agent Six and Doctor Holiday discovered Rex, he became their third option: the cure. His nanites are unique: since they came from the first batch of nanites ever created, they can reprogram other nanites to an extent. He uses this to reprogram the rogue nanites that turn people and animals into EVOs, and this reprogramming turns them back into what they originally were before mutating into an EVO. His nanites also grant him the ability to create machines out of his nanites, which he uses to combat EVOs. He can also talk to other nanites, and with the addition of the Omega-One Nanite he can control them to greater lengths. His nanites can also talk to any form of technology, so Rex is useful for hacking and other missions along those lines.   

Providence is the leading organization in the world that combats EVOs. There are smaller splinter groups (notable ones include Hunter Cain and Rombaur & Lansky) who tend to aim to destroy the EVO threat or to catch EVOs in places that Providence either can't or is too tied up elsewhere to get to. Providence is not endorsed by any world government, but is recognized and lauded by the United Nations and other countries for its international work fighting rogue EVOs.   

Enemies of Providence come in all varieties. There are splinter groups (notably the Green Fist) who believe that EVOs should be treated like normal animals and try to set them free from Providence. Others, like Van Kleiss, want Providence technology and/or want the EVOs to rule the world. But arguably one of the greatest threats to Providence is the public, the great majority of whom are seen to be easily influenced and tend to go against Providence when massive EVO outbreaks occur or when radical leaders (such as Hunter Cain) speak out and accuse Providence of not listening to the people and fighting for itself, not the greater good of the world. When the public loses trust in Providence, this can affect the operation of the organization, because many of the soldiers grew up as civilians and can relate to people like Hunter Cain, who speak out for the values of human life that "Providence seems to care less and less about".