With the right skills and equipment, you can make an unstoppable killing machine out of the Mass Effect 2 Soldier class.
When playing Mass Effect 2, 65% of people choose to play as a soldier instead of something more sneaky or biotic-y. With the second game's emphasis on shoot-em-up action, this makes sense. AIs are tricky to program and often teammate AIs leave players wishing they were all alone against the galaxy. Mass Effect 2 is no different. Your teammates aren't perfect. They aren't as quick-thinking and usually not as accurate as the player. So how can a player make an easy run of Mass Effect 2, while still deriving as much enjoyment as possible from an environment built to emphasize run-and-gun gameplay? Simple: take the role of running and gunning upon yourself and let your teammates back you up.
Tactically, the soldier should play very simple: pick off anyone dangerous with your sniper weapon. We're talking rocket guys, flamethrower guys, and the like. The sniper weapon should also be used early in a fight to even the odds before the enemy can reach cover, or before you have to get up close and personal. Once the fight does get close, use rapid fire to make enemies keep their heads down, and use your pistol plus Adrenaline Rush to deal with heavy enemies. Shotguns should be backup weapons, or used to clean up injured enemies toward the end by charging them and finishing them. The key thing to remember when playing this way is when to stand still. When attacking, you need to always be moving forward from cover to cover. When defending, choose the most appropriate cover and hold it as long as possible. Note: against husks, that defensive tactic doesn't work. Keep moving forwards and backwards, but always make progress towards getting out of the area.
The key to playing a simple soldier is equipment selection. Armor is simple: you want to take as much ammo as possible and be as durable as possible. Grab armor upgrades that reflect this. For weapons, your eventual load out should be as follows: - M-6 Carnifex Hand Cannon - M-76 Revenant LMG - M-27 Scimitar Heavy Assault Shotgun - M-97 Viper Sniper Rifle - Collector Particle Cannon
As shown earlier, each weapon serves a specific purpose. The Viper takes out long-range enemies and dangerous enemies, and helps to even the odds early. The Revenant serves as your primary weapon for almost any situation since it has lots of powerful ammo, and its rapid fire will hinder enemy movement and rip apart shields and armor. The Carnifex serves as a nice backup weapon, and easily handles many bosses when used with Adrenaline Rush, and the Shotgun will help clean up most confrontations while conserving ammo for your main weapons. The Particle Cannon serves as a backup to the Revenant for use against especially tough enemies, since it does a lot of damage quickly and is pretty conservative with your heavy ammunition.
Another important element of this strategy is choosing teammates. Pretty much anyone will do, but Biotics are always useful, as is anyone with a combat drone, so take Jacob and Tali if you are having trouble choosing.
Finally, you need to be able to withstand as much damage as possible. The armor and relevant upgrades will help with this, but at some point you will need the Geth Shield Boost, Barrier, or Fortification and as much of it as possible. When you hit advanced training, grab one of these as soon as it is available. All three will do what you need them to do, absorb damaga, so the choice is up to you.
Using this guide, you ought to be able to breeze through any challenge in the game rather quickly. Good luck, and good hunting.