With the help of the fine folks of bnet, of course. 5 hours and a lot of guest profiles
Edit- just finished Halo 4 too :3.
English
#Gaming
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343's map pack is the reason I stopped caring about gamerscore. I used to enjoy collecting them but that 3... There should be a law against not ending the achievement in anything other than a 5 or a 0. Bastards.