The Reckoning DLC added a new ending for Game over, man! Easter egg on Outbreak (or was it here since Havoc came out?)
So in the new ending, you do everything normally until the step when you upgrade your keycard. You have to use melee attacks to kill them so they drop special cards. But since Exo Slam is also a melee attack, can I use it to complete the step?
The fact that Exo Slam gives you 50 points makes me think that I can't.