The Sergeant Johnson Leader Add-on for Halo Wars 2 has 3 achievements worth 30 gamerscore.
Win 3 matches as Sgt. Johnson (Multiplayer, Skirmish or Blitz)
Use Repair Beacon special ability 15 times. (Multiplayer, Skirmish or Blitz)
Kill 50 infantry units with the Colossus' Stomp ability (Multiplayer, Skirmish or Blitz)