Ryse: Son of Rome

Double executions are when you kill two enemies at once, not to be confused with what you do in the Arena when you and a partner kill the same enemy at the same time.

The easiest way to get this achievement is when go into your focus mode (Use Jupiter God if you are in the Arena) when you start chopping up one enemy move on to the next enemy and when they both have skulls move to about the middle of the two enemies and hit RT. It should initiate the double execution.

If you wish to view your progress you can go to the X1 Achievement section and check out your achievements for Ryse, go to the Double-Down achievement and it should have a counter as to how close you are to the needed 50.

Simple, do 50 double executions in any mode.
The best mode is in 6 chapter, when you is defend ROMA.

Can you see this video, when i explain in PT-BR.
Thanks

Another "farming" location is at chapter 3, Trial By Fire, when you're supposed to stop the barbarian counterattack.

You get to choose between two alternatives, choose the one where you go in with melee support though with arrows coming at you, BUT, that's the nice part, you will actually take advantage from the arrows.

Easy as peasy, gather some dudes, make them stay inside the red circle, the arrows hit, and suddenly they all have skulls above their heads.

Have fun!