You Are the Support, Son (10)

Successfully defended COG headquarters

It's good to be supportive. Follow the story through Act 5, Chapter 2 on any difficulty to get this one.

Brumak Rodeo (10)

Captured a Brumak

Followed shortly by Brumak square dancing. Follow the story through Act 5, Chapter 4 on any difficulty to get this one.

Does This Look Infected to You? (10)

Defeated the Lambent Brumak

It's so shiny! Follow the story through Act 5, Chapter 5 on any difficulty to get this one.

That's it for the story achievements. Now for the difficult achievements. Like the original Gears, the difficulty achievements stack, so if you do your first run through entirely on Hardcore, you'll get the achievements for Hardcore, Normal and Casual. The Insane difficulty level is unlocked upon completing the game on any difficulty level. When playing in co-op, each player can set their difficulty level independent of the other, a fact we'll use later on. It goes without saying that to get the achievement for a particular difficulty level, the entire game must be played at that difficulty level, but I went on and said it anyway. I'm crazy like that.

Tourist of Duty (25)

Complete all campaign acts on Casual Difficulty

Unless you've never played any video games ever, there's really no point in playing through the game on Casual to get this achievement. Just play through on Normal and rock the twofer.

Guerrilla Tactician (50)

Complete all campaign acts on Normal Difficulty

Normal is a good place to start so that you can unlock Insane. It's plenty easy, similar to Casual in the original Gears. Oh sure, you still can't run out all willy nilly but if you stick to cover and line up your shots, you should get through things no problem.

Artist of War (75)

Complete all campaign acts on Hardcore Difficulty

Hardcore gives a bigger challenge than Normal, similar to hardcore in the original Gears. Clearly, you can do what you want, but if you're planning on doing the game on Insane, save yourself some time and skip Hardcore, unlocking Insane with a Normal run instead. Then, when you do Insane you'll get this one free of charge, or in the interest of irritating tongue clucking grammarians everywhere, "for free".

Suicide Missionary (150)

Complete all campaign acts on Insane Difficulty

Insane in Gears 2 is more difficult than Insane in Gears 1. If you want the challenge legitimately, by all means, go for it and more power to you. If, however, you just want the achievement with less effort, take advantage of the fact that when playing the campaign co-op, you and your partner can set independent difficulty levels. You play on Insane and they play on Casual. They take point and slaughter everything while you hide like a scared child. Oh sure, in some cases you'll have to split up and earn your pay, but there aren't a lot of those times, and you should be able to handle it. As Marcus is the designated driver for any driving section, make sure that the person picking the Casual difficulty level hosts. If you can't find a co-op partner, you can do the split screen co-op thing with another controller, being sure to hide the Insane you while the Casual you kills everything. Insane you will catch up automagically as you progress through the checkpoints; however there will be times where you have to have Insane you kill things. Confused? I know I am.

Friends with Benefits (50)

Complete all acts in co-op on any difficulty

Not only is the game more enjoyable with another person, but you get 50 points for doing it from start to finish co-op style. Yay for you. For any of the co-op achievements, you can go play the acts and chapters in any order you want. So, if you play all but say, Act 3 in co-op, you can go back and play Act 3 co-op once you've finished the game and get this achievement.

Once More, With Feeling (10)

Mastered the ways of the Active Reload

For this one, perform 30 Active Reloads in any mode. To do an Active Reload, press the right bumper and then watch the white bar under your ammo count in the HUD. When the white cursor ends up in the small white space on the bar, hit the right bumper again. You get a damage boost and credit towards the achievement. Active Reloads are a big part of being successful in Gears so chances are you'll get this one as you progress through the game, but if you're an impatient little imp, just fire one round from your pistol, do an AR and then repeat 29 more times.