Do not go rushing out! This might seem dumb but trust me on this. Later on in the game this will help you and save you lots of life. Taking your time and looking ahead of you helps. Running ahead when the SWAT or Army is after you only leads to a quick death, as they deal tons of damage in a short time.

Standing is a no no on Extremist. The AI is insanly dumb, use this to your advantage! Crouching causes the AI to miss an insane amount. I'm not joking, I cake walked the entire last half of the game just from using crouch. Standing gets you hit a lot. Using the aim lets to see farther, allowing you to pick off enemies easily with no troubles at all!

Don't forget to use burst firing or single (tap) shooting. This keeps your accuracy high, as well as not waste much ammo and take out your enemies much quicker. *Thanks Zer0Point for reminding me of this! ^_^

When the SWAT or Army start to show up and you're not sure if you can take them all. Go camp in a building and let them come to you! Sit in a corner and watch the door, run into the Vault at the bank, run into a room with ammo or body armor. The enemie's AI is stupid, and they will walk through the door one by one and you can easily take them down. Don't forget to crouch! When you crouch the AI might forget to even shoot at you!

Yes you need to kill a lot of civs to progress through the game, but don't kill them all! You will need them for health if you die and respawn! If you so happen to get swarmed or run out of ammo, or brush up against a moving vehical, you will respawn (providing you have a token) but with hardly any health. If you don't kill everyone you see, you can pick up on ones you passed by and regain your health before you fight the cops/SWAT/Army again.

Maybe you are about to get swarmed, bug out then! It might be your best interest to run back to an area you just cleared out, or to another spot you used to take advantage. A good example I can provide is the 4th level, Train Station. When you are leaving the train station, the Cops, then SWAT, then Army shows up to stop you. I found that when the army showed up, they were almost too much for me. However! Going back up the catwalk going across the tracks was a super easy way to lead them down 1 path and take them down much easier.

That was what I did and completed this game with no problems!

Did I miss anything, or need help on a certain part! Let me know and I can add more to this guide for you all!
~Aythadis