The Operation: Spearbreaker Add-on for Halo Wars 2 has 5 achievements worth 40 gamerscore.
Gain a gold medal and complete all objectives in ‘Gatecrashers’ on legendary
Gain a gold medal and complete all objectives in ‘Not On My Watch’ on legendary
Complete Operation: Spearbreaker on any difficulty
Complete Operation: Spearbreaker on Heroic difficulty
Complete Operation: Spearbreaker on Legendary difficulty