Long before the Prothean ruins on Mars were discovered, humanity was kicking ass and chewing gum with what is considered the blueprint for all warriors: the Soldier.
Keep your biotics and put those omni-tools away. They won't be needed. The requirements for playing a soldier are as follows: grit, determination and guns, lots of guns.
The measuring stick to which all other classes compare, Soldiers can absorb more damage than any other class. Even more so when complimented with the bonus powers Barrier, Fortification, or Geth Sheilds. Add in four handy ammo powers and the ever useful Adrenaline Rush and Concussive Shot and what you get is one man army.
-Adrenaline Rush Mass Effect 2's version of Bullet Time, Enhanced Reflexes or The Matrix. Basically, the slowing of time so you can nail those perfect head shots. Additional points put into this power can increase the duration. It is the essential power on Hardcore and Insanity playthroughs.
-**Concussive Shot Just as the name implies, this power fires a high-impact round that can stun and does a good deal of damage to health and biotic barriers. Not as useful for shields or armor,Concussive Shot is better paired with biotics such as Pull or Stasis to maximize effectiveness.
-**Disruptor Ammo A Geths worst nightmare, this ammo power is perfect for mowing down hordes of mechanical baddies. Its shield-stripping abilities also means that Disruptor Ammo is highly effective at making most foes wish they had researched better shield upgrades.
-**Incendiary Ammo Burns holes in enemy armor faster than Conrad Verner can name drop Commander Shepard. Incendiary Ammo chews armored foes to bits. It comes with the added bonuses of setting your enemies on fire and preventing those annoying Vorcha and tough-as-nails Krogan from regenerating health.
**-Cryo Ammo Colder than the average blizzard on Noveria, Cryo Ammo is a terrific form of crowd control. What this ammo power lacks in direct damage, it makes up for in the ability to insta-freeze your targets in place. Setting them up for a nice Concussive Shot to shatter their dreams of retiring early and collecting money off of short-selling prefabs.
**-Combat Mastery The only passive power on this list, Combat Mastery defines what kind of bad ass you get to be. With Commando leaning towards damage dealing and Shock Trooper geared more for receiving damage, the choice is entirely up to you.
Effective Soldiers are best paired with anything but another Soldier. Biotics and Tech skills can set up or finish off enemies quite nicely when paired with a Soldiers ammo powers. Just be sure to take the brunt of the damage for your squad. Simple enough considering practically the entire galaxy wants you dead...again.