Neuroscience

Reach: kill 10 enemies with headshots in a matchmaking game. Complete.

Unto The Breach

Reach: Daily Challenge - Kill 125 enemies on Corvette in Firefight Matchmaking. Complete.
And in one round of Score Attack there are less than that. Hard couple of rounds by myself.

Hyper Lethal Vector

Reach: Daily Challenge - Kill 200 enemies with headshots in Firefight Matchmaking. Complete.
Nothing like some Grunpocalypse.

A Simple Spree

Reach: Daily Challenge - Earn any spree in Firefight Matchmaking. I am almost ashamed to claim this 2000 credits.

Blasting and Relaxing

Reach: Daily Challenge - Kill 180 enemies in any mode. Complete. Few credits to help get the last two objects in the armory and eventually max out my rank.

In Your Face

4: War Games Daily Challenge. Earn 10 CQC medals. Complete. But the 1000 XP was hardly worth the effort.

Combat Opportunity

4: War Games Commendation.
I usually don't notice the commendations mid game. But this one I did. I have mastered the combat opportunity medals. And less than 6 months after the release of this game.