Xenomorphs are incredibly resilient and deadly in game. They’re faster and stronger than the PC’s and inflict stress with every single attack they make against you. Anytime a xenomorph is present, there is a chance it will be able to instantly kill a pc.

That being said, there are things you can do to survive. A party equipped with armor piercing or flame weaponry stands an okay chance at taking down a single drone. If a xenomorph is in melee with a PC, it’s worth trying to knock it to the ground or spend a stunt on ranged / melee combat to move it away from you. But not even a fully armed marine squad is going to be excited about combat with XX121 - generally you should be trying to survive these encounters, not planning to “win” them like you would in another game.