So what voltage does the Venom charger say it has, how low did you run it?

If its under 3v/cell, I would try to charge it as a NiMh at 0.5 - 1amp. Only charge it until the voltage is back up over 12v and maybe a little more. Stop charging and then try charging with proper 4S lipo settings. If you haven't damaged it, this will work. This technique has saved a lot of overdischarged lipos.