To unlock this achievement you need to be playing as the God Janus.
You need to hit two enemies with his ultimate (4 or
) at 'max range'.
This is misleading, and I can't really tell you what max range is as Janus' ult can traverse entire maps.
I've included a video of where I earnt it. You can see I hit Raijin and then Chaac runs into it. To give you an idea of distance. They weren't hit at the same time.
The ability doesn't need to have more than one level point in it. Kills do not matter.