Human antagonists
Sam works for a group called the United Cities of America (UCA), that is trying to restore something close to the USA. However, several groups of people obviously have very different objectives.
Cliff and his friends
The most notable of the human antagonists in Death Stranding is Cliff, which can be seen in the first trailers, emerging from a pool of black liquid, followed by skeletal soldiers with red eyes. He can also be seen with a tank covered with tentacles and organic matter in another trailer. He seems to know a lot more about Death Stranding than anyone else.
The fact that he does not use Bridge Baby or mechanical arms like Sam, but rather conventional equipment suggests that he sees humans as his enemies, or at least as threats, rather than BTs.
Homo Demens & Higgs
Armed separatists seeking to maintain the independence of Edge Knot City, a city on the West Coast. They are detaining Amelie, who should have become the new president of the United Cities of America (UCA). The most important representative of this organization is Higgs, the man in the golden mask.
Unlike Cliff, he and his men use equipment that is quite similar to Sam's, although there are some differences in their design. They also seem to engage in extremist actions, such as deliberately provoking a voidout to eliminate the UCA. They also use conventional firearms against other humans.
Mules
These enemies, recognizable by their yellow hazmat suits, like to ambush Sam during his deliveries. They can also be found in camps in the wild. These people are suffering from a mental illness called "Delivery syndrome", they steal goods and various objects before storing them in their camp.
However, they do not kill human beings, which explains why they are seen using electrified javelins in The Drop trailer, and not just putting a few bullets in Sam's back. Likewise, Sam uses his electrified bolas to immobilize them.
Mules have a special detector that targets cargoes, which helps them locate Sam and his colleagues. But if you approach them without cargo, this detector will not react, even when you enter their camp. The mules are afraid of BTs, and if they are close or the timefall starts, they will retreat.
