Having the Queen lead major assaults is a valid tactic, especially once she's been upgraded with the army-buffing 'War Empress' trait.

Authority Equals Asskicking: The Alien Queen is one of the the strongest units in the Alien lineup only surpassed by the Ravager in terms of attack power.

The Alien Ravager, however, conspicuously subverts this - It will always kill its victims outright via decapitation, preventing later impregnation. They never recover from this state, however, so they are still considered dead for gameplay purposes.

As Lethal as It Needs to Be: Despite possessing deadly claws, teeth, and blades, Alien attacks merely render their victims 'comatose' so they can be dragged back to the hive for impregnation.

Artificial Stupidity: Terrible pathfinding AI, leading to units going on mile-long walks when the player's not looking, missing perfectly serviceable doors, etc.

Meanwhile, the predators kidnapping Kadinsky leads to the attempted rescue mission in Marine 7. The best example is the destruction of Kadinsky's lab - the attack is part of Predator 6, and leads directly to Alien 5 after a stray plasmacaster bolt breaks the lock on a specimen containment cell.

Another Side, Another Story: The three campaigns are roughly parallel to each-other, and many levels in each campaign involve dealing with the ramifications of events that occur in the other two.

However, their units are fairly fragile and rely on a Queen to lay eggs and impregnate hosts with chestburster, which take time to incubate. The Aliens have the largest population of the races and typically Zerg Rush the opposition. They're reliant on a slow-moving Shrine to call down reinforcements via drop-pods, and they deploy faster than any other race. However, all Predator units can cloak and heal themselves at will by spending energy that regenerates over time. The Predators have the smallest population cap and each unit is fairly expensive. They're capable of fielding more troops than the Predators, but not as many as the Aliens and are reliant on Commtechs to call in reinforcements at designated drop zones.

The Marines lack melee units, but make up for it with a wide roster of powerful ranged and utility units.

Achilles' Heel: The Aliens possess a vulnerability to fire, it does extra damage to their units and negates any regenerative abilities they have.The radiation they put out stops the Xenomorph's Healing Factor. Abnormal Ammo: The marine Flame Trooper and Smartgunner can be upgraded with cobalt-60 ammo.

Xenomorph vs xenomorph avp extinction