You want a powerful weapon?
Here it is:
Barrett .50 cal (source)
This rifle is capable of taking out lightly armored vehicles and helicopters. And here’s why:
Round Comparison (source)
The AK-47 round is the 7.62×39 (4th from left). The .50 cal is the last round on right.
I’m a fan of the AK-47 but as others have stated it’s not as powerful as it’s made out to be in non-military or non-firearm circles. There are other weapons that are much more powerful, able to reach out and kill for miles whereas the AK-47 is only accurate for 300 yards or so. The size of the cartridge – the case holding propellant – shows why.
See also the thread: What is the difference in lethality between 5.56, 7.62 and 50 cal?