>>95821499
Xenomorphs are good antagonists for a horror campaign.
They may not match supers in terms of raw power, but their ability to use the environment to their advantage makes for excellent ambushers, allowing them to pick heroes off one by one.
They make for good long-term thread that requires research to locate the nest, and firepower to clear it, since leaving even a single drone would mean having to start it all over.
They are a growing persistent threat to the PCs, as well as civilians. And they must be dealt with ASAP, since every day wasted means more people are caught and used to spawn more drones.

Predators can't remember the name atm on the other hand, might be a match for lower rank physical supers, and further build upon it with tech and hunting skill to be a worthy opponent even to some of the higher rank capes.
They are best served as one-off or a recurring unaligned antagonist group that simply hunts the PCs as the most dangerous game in town.
Some sort of Great Hunt event could be used to make them a more long-term threat, where PCs are repeatedly hunted and have to find some way to drive them away. A kind of a toned-down alien invasion campaign.