List of Achievements for Halo 4
From Halopedia, the Halo wiki
There are a total of 86 achievements in Halo 4, which are worth a total of 2,000 Gamerscore. The game was released with 49 achievements worth 1,000 Gamerscore. Eight more achievements worth 250 Gamerscore were released with the Crimson Map Pack. Another ten achievements worth another 250 Gamerscore were released with the Majestic Map Pack. The Castle Map Pack includes 9 achievements and 250 Gamerscore. The Champions Bundle includes a final 10 achievements and 250 Gamerscore.
With the addition of the Champions Bundle, Halo 4 featured both the greatest number of achievements (86) and highest gamerscore (2,000) of any Halo title until the release of Halo: The Master Chief Collection, which exceeded it in both categories (500 achievements worth 5000 gamerscore).