As in real life, there are rarely Good and Bad teams. Anyone could be seen as the enemy, it is all a matter of perspective. Additionally not every nation or faction subscribes to the idea of a uniform or organized army.
Some factions like the People’s Guard are largely based on a core of volunteers and local Militia. These efforts are all funded by pre-collapse gangs and cartels who have used their considerable wealth to hold onto and multiply their grip on the city after the official Governments have fallen to shambles.
Other factions like The Watch are little more than a loose association of independent vigilantes. Each of their leaders controls their own Neighbourhood Watch and functions largely without any sort of oversight leading to large amounts of in-fighting. Many of The Watch’s sub-factions are aligned with or against Kurtz and others choose to avoid the conflict whenever possible.
Factions like The Morlocks subscribe to an anarchist lifestyle choosing to abide by a “no rules” rule and elect their leaders through barbaric fights to the death. They aren’t all bad though, as Heimlock wasn’t always a Morlock, but they are the only ones willing to look past his checkered history. There are also unspoken ‘rules’ as even choosing the wrong benefactors can get you exiled, as Cross has found out the hard way.