Similar to my solution for the achievement “We Few, We Happy Few…” this is more of a heads up than an actual solution. Just wanted to let everyone know you can get this achievement by using only two gamertags with guests signed in. Just got the achievement using this method so if you can’t get four people at once or just want to tackle it with yourself and one or two friends this is the option for you. The guests don’t have to be active just them being in the game will give you credit. Mutators can also be used.
How to sign in your guest to XBOX Live: Make sure to have the second controller on then press “Y” on the second controller to login guest. After that you will have noticed that your guest is signed in but only for local. You need to press “Y” again (on the second controller) go down to the very bottom and select “Guest.” After that you will be returned to the main menu and your guest can be used on XBOX Live.