You may be interested in reading my Mass Effect 2 combat Guide, for more general information.
Anyone who’s played mass effect 1 should be familiar with the enemy in this boss battle! They are the reason you avoided anomalies, maybe you killed one or two of them… while in an infantry fighting vehicle. Now you need to kill a thresher maw on foot. Of course, you could just do what the shaman says and survive this boss fight… but then you wouldn’t be looking at this guide would you?
You’ll be pleased to know that the Thresher maw is not hard. First of all, you’ll notice that he only has an armour defence- this is very useful as it means you only need to use one set of powers to bring him down! Power such as warp and incendiary ammo are the best for racking up the pain on the thresher maw boss, but even grunt can do some serious damage with his basic attacks.
Also, it goes without saying but Shepherd should be using his heavy weapon. I used the collector beam laser when I first encountered the thresher maw boss, and it served me well. Everyone else should use long range weapons for the boss fight against the thresher maw.
As for actual tactics to use in this boss fight, there are only two that spring to mind. First of all, when the thresher war digs, you can tell where he is going to pop up by looking for where the rubble rising from the ground a few seconds before the boss pops his head up.
Secondly, jink left and right as you fire, and when the thresher maw takes a shot at you, stop firing and keep moving to dodge the attack.
Beyond that, there’s not much more that this boss fight guide can tell you- just keep moving, keep using anti armour powers, keep shooting with heavy weapons and strafe left or right to avoid attacks. Keep this up and even on higher difficulties you should be able to kill the thresher maw in under two and a half minutes. Now the mass effect achievement big game hunter is yours- you’ve killed the biggest predator on Tuchanka!