It would be unworkable since the second blade would merely add weight. A person may easily miss their aim while wielding an axe the size of Mjolnir, because the tremendous weight just knocks them off-balance. When it comes to history, video games and movies may be quite deceptive. Yes, but only the Amazons utilized them. They were also very rare tools used by the queen herself. The fact is that these massive weapons were created mainly for show. In reality, most tribes in prehistory didn't have such resources at their disposal. The Amazons may have been an exception because they got a lot of practice fighting each other with them. But otherwise, they were too expensive for common people. In case you're interested, an average-size modern European or American man could lift about 50 pounds - this includes the axhead itself. So yes, double-headed axes were definitely not a lightweight equipment. However, they weren't so heavy either. Since they consisted of only one piece of wood, they could weigh less than half as much as an ordinary hatchet. Also note that not all double-headed axes are equally large. Some were actually smaller than normal ones. These were used by warriors who wanted to show off their skill without intimidating their opponents. In conclusion, double-headed axes were useful tools in their time and place. However, they were not commonly used by other cultures before or after the Amazonians.