Leviathan was a Russian Hydra, basically. Meanwhile, we have a Russian scientist working with Stark who betrays him at some point and tries to sell his tech to America's Cold War enemies.
Also...I mentioned in another comment that the symbol looked like the symbol for Aries. In the comics...guess who was instrumental in the founding of Leviathan and Hydra/SHIELD? That's right...ARIES. he formed the Great Wheel, to share stuff between groups...then the Russians betrayed him and formed Leviathan and Hydra/SHIELD formed as well. Obviously, it can't be the exact same story as the comics...but I think that Leviathan has formed (obviously), Aries is working against them for his own reasons (maybe something to do with the Zodiac Cartel...because...you know...the Zodiac serum was in the One Shot).
EDITED TO SAY: Looking at the drawing the guy made in the dirt...it really doesn't look as much like the Aries symbol as I first thought (the squiggly line looks deliberate, the "horns" aren't as pronounced)...so maybe there is a Serpent Society link or something...but for the moment, I'm sticking with Zodiac. Also, in Agents of SHIELD, Blake asked May if she is a Scorpio...and it seemed like such a forced conversation that it seemed like they were hinting at it.