The Marines simply have no answer to these - especially the Predator's wildly overpowered stealth - and the woes of the human soldiers don't end there. They are vastly inferior to their extraterrestrial enemies in mobility, too, with the Aliens able to run at lightning speed up walls and along ceilings (although not without some disorientation), and the Predators having a neat "focus jump" that allows them to target and leap to useful vantage points, like branches and overhangs. The Marines' ranged superiority isn't the consolation you might think; they might have assault rifles and shotguns, but Predators get mines, throwing discs with after-touch, and explosive lock-on missiles.
The species are more evenly matched in one area which AVP exploits better than many shooters - visibility. Predators have thermal visors and easy access to high vantage points, Aliens have a sense which allows them to see outlined enemies through walls, and Marines have their iconic, pinging motion detectors, whose radar blips are the best line of defence against a cloaked Predator.
Rebellion has described the single-player Marine campaign of AVP as "survival horror", and that's pretty much the multiplayer experience for the hapless humans too, only with a bit less survival. But what doesn't work in deathmatch - which, like all of AVP's modes, supports 18 players - works much better in Infestation and Predator Hunt.
In the former, a variation of Last Man Standing. all but one player starts as a Marine, with the other starting as a solitary Alien. Every Marine killed then comes back as an Alien, and since they get infinite respawns, the tide of Xenomorphic death can't be stopped - only delayed until you go down in a blaze of glory assisted by a last-minute weapons drop.
In Predator Hunt - and you need no further indication of how overpowered the Predator is than this - there is only ever one Predator, with the rest of the match taking the role of Marines. Whoever manages to kill the Predator becomes it, and the goal is to secure the most kills as the Predator for the glory of the hunt.
Purely through the character and abilities of the three species, both these modes create great, spontaneous recreations of classic Aliens and Predator moments. Infestation had Marines with their backs together in a panicked huddle, defending against a multiplying horde of Xenomorphs (this will also be replicated in a four-player co-op mode that we didn't get to try). In Predator Hunt, we found ourselves hunting suspiciously for a lone Predator over tense, quiet minutes, until he suddenly materialised in our midst, strangling one of our number, and all hell broke loose.
At times like these, you're reminded that Rebellion has a long history with and great enthusiasm for this material - it made the 1994 Atari Jaguar and 1999 PC games, as well as a recent PSP movie spin-off. It knows exactly what being a Marine, Alien or Predator is supposed to feel like: feeling your heart rate double as the pinging of your motion sensor does; racing upside down through tangle of shadow; swooping, cloaked, on your prey from a high branch. Perhaps that's more important than balance overall, but if AVP is to contend with its multiplayer rivals when it launches next year, Rebellion will need to find one without sacrificing the other.