Command & Conquer 3: Tiberium Wars/Scrin Units

Disintegrators

 * Cost 300

Assimilator

 * Cost 500

Shock Troopers

 * Cost 800

Stormrider
Cost: 1500 Credits

Counter
The best way to counter the Stormrider's full attack capacity is NOT to destroy the Gravity Stabilizer it's stationed at, but to just throw whatever anti-air you got at it. You're guaranteed that your missiles can deal a ton more damage than it's pulse cannons.

Devastator Warship
Cost: 2400 Credits

Counter
The Devastator Warship is easily countered with air-based anti-air, provided that the Devastator isn't escorted.

Planetary Assault Carrier

 * Cost 3000

Counter
The Planetary Assault Carrier is easily countered by first taking down the eight sub-aircraft that it launches at you. Then while it's spawning a new replacement, hit it with your anti-air hard and fast to quickly take it down.

Mothership

 * Cost 5000

Counter
To counter the Mothership takes nothing short of a miracle (or a ton of Firehawks if you got access to them). Heavy armor, a really powerful gun, but slow as hell, making them perfect targets to throw whatever anti-air you got at them.