Gamer has been removed
I was confused on how to get this so I'll explain it clearly.
Each time you go to a view point, rescue a citizen, or complete side objectives you get a block increase on your */15 bar. Once you've done 15 objectives those bars become one on your main sync/health bar.
So you've got to do quite a few side objectives to get this. I did my fair share and completed the game and still didn't get it but you can go back after and get it once you're finished.
So I'll just restate, when you complete and objective you'll see a */15 bar pop up get that to 15 to add another bar to your main sync bar the */15 will reset to 0, do 15 more objectives to get another.