From Halopedia, the Halo wiki
In Halo Wars Douglas-042 is exclusive to the campaign and always has an M41 rocket launcher. Like the other Spartans of Red Team he can be revived if killed.
Halo Wars 2
In campaign Douglas-042 acts the same as he did in Halo Wars, barring Spartan slam. In Multiplayer Douglas-042 is exclusive to Ellen Anders and can be built at the UNSC Armory. Unupgraded Douglas starts off dual wielding M6C magnums and is great against infantry, but only okay against vehicles, aircraft, and structures. Once upgraded with an M41 rocket launcher Douglas will be effective against vehicles and aircraft. In Blitz Douglas-042 costs 230 energy and features the Guard ability that agros enemy units, forcing them to attack Douglas-042.