In my playing of Destiny on Xbox and PlayStation I have earned each of these medals except #1. Here we go.
9. Enemy of my enemy (3 crossfires in one life)
8. Clutch (Win after trailing with 2 seconds remaining)
7. Won't be Beat (Win a rumble match after trailing by 500 or more when the enemy is nearing victory)
6. Bulletproof (Win a match of elimination without anyone on your team dying)
5. Sum of all Tears (Win a rumble match with a score higher than everyone else combined)
4. Phantom (Kill 7 enemies without taking damage)
3. Mark of the Unbroken (Get 15 kills in a single match without dying)
2. We ran out of Medals (Get a 25 kill streak)
1. Seventh Column (Rapidly kill 7 enemies)
Disclaimers:
1. I believe Reaper could be on here, it isn't because it is part of Seventh Column
2. Both Sum of All Tears and Bulletproof can be earned when enemies leave, on Xbox I earned 3 bulletproof medals from another fireteam leaving immediately. Sum of All Tears can be easily earned if a few people leave the match and you win with only a couple people in the match
3. Most of these medals can be "boosted," this is known but not taken into consideration. So don't tell me how a certain medal can be earned if your friends do something for you in a rumble match.
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Sum of All Tears is pretty easy if you go in Year One rumble. I got my SoAT about two months ago during Hand Cannon meta using No Land Beyond on The Anomaly. Call me a legend.