A Parting Gift (20)

Killed 10 enemies with a grenade while down but not out

This one requires a bit of set up. First of all, you need a frag grenade equipped. Then, you have to be downed. Then, an enemy has to approach you with the intention of executing you before you bleed out. Once they approach you, you'll see a prompt on your screen to pull the right trigger. Do so and you'll blow up both yourself and your enemy, getting credit for the kill no less. Obviously, with as much set up as this requires, you're probably not going to get it in the campaign or in Horde mode, not without getting killed a whole bunch in the process. Instead, use the two controller method as with "Organ Grinder" or use a friend as with "Crossed Swords".

Pound of Flesh (10)

Used 10 meatshields to survive

This one also requires a bit of set up. Basically, you have to use a meatshield to save you from something that would have normally killed you, like a grenade or other explosive device. Carrying around meatshields in the campaign while you look for Boomers can be time consuming and smelly as the Locust are not known for their personal hygiene. Better to use either the two controller method, or another person. Either way, here's the best way to go about things. Down an enemy by smacking them upside the head a couple of times. When they're downed, switch to a frag grenade and press B to grenade tag your downed opponent. Once you've tagged them, immediately press the A button to pick them up as a meatshield. The grenade will go off and you'll survive, although desperately in need of a shower.

Kick 'Em When They're Down (10)

Executioner with style

For this one you'll have to perform all 11 unique executions on a downed enemy. Rather than have yourself running out from behind cover in the campaign, with the intention of executing all of the downed enemies, and getting yourself killed in the process, go the local multiplayer route for this one, either with a friend, or a second controller. Here's the list of the weapons that you can do executions with and the associated button to press:

Seriously 2.0 (50)

Kill 100,000 enemies (any mode)

The good news about this achievement is that kills count from all modes. The bad news is that it's still going to take you a bunch of time. This should be the last achievement you go for, once you've gone though the campaign however many times you're going to through it, after you've done Horde mode to level 50, after you've played all of your multiplayer matches. Once you're ready to tackle this beast, load up Act 1, Chapter 4 on Casual, get on Betty's turret and start shooting all of the Locust coming out of the hole in the ground. Once Betty has turned so that the Brumak is blocking your view, load the checkpoint back up. With this mode you can get about 100 kills in 2 minutes. 30 hours later and this baby is yours!

Back to Basic (10)

Won all Training Grounds matches

The From the main menu, you'll see the Training Grounds option. In here you'll find five different matches. Win all of the matches and this one is yours. The bots that you're teamed up with are fairly ineffective, so you'll have to do a lot of the work yourself. Don't go running in all Rambo style and you should be fine.

Around the World, Again (30)

Won a match on every map shipped with the game

For this one, load up a local Warzone map with 1 round and 10 minute rounds. Invite either a friend, or use a second controller. Once the match loads, make your way to your friend, or unmoving stooge, and kill them. Once the match ends, pick the next map and do it again. For this one, you only have to win with the maps that come on the game disc, not the ones downloadable ones that came from the one time use code received for buying the game new. The list of shipped maps is:

Kick 'Em When They're Down (10)

Executioner with style

For this one you'll have to perform all 11 unique executions on a downed enemy. Rather than have yourself running out from behind cover in the campaign, with the intention of executing all of the downed enemies, and getting yourself killed in the process, go the local multiplayer route for this one, either with a friend, or a second controller. Here's the list of the weapons that you can do executions with and the associated button to press:

Standing Here, Beside Myself (10)

Win 3 matches of Wingman (public)

This one has to be done in a public match, so get a good partner, or just hope that you get paired up with a good partner. Win three matches and you're all set.

Beat the Meatflag (10)

Capture 10 meatflags in Submission (public)

Another public match achievement. Remember, it's not enough to grab the meatflag, but you have to drag it back to your base. Good luck with this one, as everyone on your team is probably trying to get it too, and more than happy to watch you die as you drag the meatflag along.

It's Good to be the King (10)

Win 10 rounds of Guardian as the leader (public)

Go into a public match, win a match of Guardian as the leader and then do it nine more times. Simple!

You Go Ahead, I'll Be Fine (10)

Win three matches of King of the Hill (public)

Your team has to win this one, not just you, so maybe you'll get lucky and get on a team that knows what they're doing.