Here is my guide to play as a soldier in Mass Effect 2.
To play as an excellent soldier in Mass Effect 2 fallow these tips. Try to have a biotic or two in your squad. Use their abilities if it starts to get difficult.
Most of the time you should use your M-76a Revenant Machine Gun or if they are at super long range use your Adrenaline Rush by pressing Y, triangle, or your key on your keyboard.
Then put a few shots through their head it should put them down. One option but you should only use on week enemies is to use Adrenaline Rush and rush them and melee them. For mecs or heavy mecs always aim for the head. It takes them out quicker.
For your ammo you should use incendiary ammo and level it up so your whole squad can use it. Don’t waste your points on the other ammo types. Also only use your heavy weapons until a boss fight the best heavy weapon is the M-920 Can.
You have to charge it up until you use it that’s why you save it up. That is my guide to destroying the Collectors and Reapers as a solider.