A gameplay enhancement mod which turns the game's main antagonist faction into a formidable foe, as well improving the game's overall gameplay.
In Half-Life 2, while assaulting Nova Prospekt, if you spawned citizens nearby your antlions, both parties will attack each other, regardless of the player's control over the antlion.
This is understandable, since Valve did not intended to have rebels fighting alongside Antlions.
This is not the case in Badass Combine, however. Here, you can have Resistance fighters and allied Combine forces coexisting with your antlions.
Some special notes:
1) You can spawn Resistance medics, demonstrated from beginning, but confirmed at 00:43.
2) Antlions no longer one hit kill Combine Soldiers, this is best evidenced at 01:03.